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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0808.1552 | Hongbao Zhang | Hongbao Zhang | Note on the thermal history of decoupled massive particles | JHEP style, 4 pages, to appear in CQG | Class.Quant.Grav.25:208001,2008 | 10.1088/0264-9381/25/20/208001 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This note provides an alternative approach to the momentum decay and thermal
evolution of decoupled massive particles. Although the ingredients in our
results have been addressed in Ref.\cite{Weinberg}, the strategies employed
here are simpler, and the results obtained here are more general.
| [
{
"created": "Mon, 11 Aug 2008 18:25:30 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Zhang",
"Hongbao",
""
]
] | This note provides an alternative approach to the momentum decay and thermal evolution of decoupled massive particles. Although the ingredients in our results have been addressed in Ref.\cite{Weinberg}, the strategies employed here are simpler, and the results obtained here are more general. |
2103.09870 | Leonardo Gualtieri | Lorenzo Pierini, Leonardo Gualtieri | Quasi-normal modes of rotating black holes in Einstein-dilaton
Gauss-Bonnet gravity: the first order in rotation | 13 pages, 3 figures, 1 table. Typos corrected and references added | Phys. Rev. D 103, 124017 (2021) | 10.1103/PhysRevD.103.124017 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational spectroscopy - the measurement of the quasi-normal modes of a
black hole from the ringdown signal of a binary black hole coalescence - is one
of the most promising tools to test gravity in the strong-field,
large-curvature regime, but without the knowledge of the black hole
quasi-normal modes in specific cases of modified gravity theories, only null
tests of general relativity are possible. More specifically, we need to know
the modes of rotating black holes, because typical compact binary mergers lead
to black holes with large spins. In this article we compute, for the first
time, the gravitational quasi-normal modes of rotating black holes in a
modified gravity theory, up to first order in the spin. We consider
Einstein-dilaton Gauss-Bonnet gravity, one of the simplest modifications of
general relativity in the large-curvature regime. We find that the shifts in
the mode frequencies and damping times due to general relativity modifications
are significantly magnified by rotation.
| [
{
"created": "Wed, 17 Mar 2021 19:15:06 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Mar 2021 17:58:28 GMT",
"version": "v2"
}
] | 2021-06-16 | [
[
"Pierini",
"Lorenzo",
""
],
[
"Gualtieri",
"Leonardo",
""
]
] | Gravitational spectroscopy - the measurement of the quasi-normal modes of a black hole from the ringdown signal of a binary black hole coalescence - is one of the most promising tools to test gravity in the strong-field, large-curvature regime, but without the knowledge of the black hole quasi-normal modes in specific cases of modified gravity theories, only null tests of general relativity are possible. More specifically, we need to know the modes of rotating black holes, because typical compact binary mergers lead to black holes with large spins. In this article we compute, for the first time, the gravitational quasi-normal modes of rotating black holes in a modified gravity theory, up to first order in the spin. We consider Einstein-dilaton Gauss-Bonnet gravity, one of the simplest modifications of general relativity in the large-curvature regime. We find that the shifts in the mode frequencies and damping times due to general relativity modifications are significantly magnified by rotation. |
gr-qc/0608005 | Ngangbam Ibohal | Ng Ibohal | Non-stationary de Sitter cosmological models | 11 pages, Latex. International Journal of Modern Physics D (accepted
for publication) | Int.J.Mod.Phys.D18:853-863,2009 | 10.1142/S0218271809014807 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this note it is proposed a class of non-stationary de Sitter, rotating and
non-rotating, solutions of Einstein's field equations with a cosmological term
of variable function.
| [
{
"created": "Tue, 1 Aug 2006 09:33:17 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Jan 2009 04:42:21 GMT",
"version": "v2"
}
] | 2009-07-22 | [
[
"Ibohal",
"Ng",
""
]
] | In this note it is proposed a class of non-stationary de Sitter, rotating and non-rotating, solutions of Einstein's field equations with a cosmological term of variable function. |
1401.7544 | Eduardo Bittencourt | E. Bittencourt, V. A. De Lorenci, R. Klippert, M. Novello and J. M.
Salim | Analogue black holes for light rays in static dielectrics | 5 pages, 1 figure | Class. Quantum Grav. 31 145007 (2014) | 10.1088/0264-9381/31/14/145007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Propagation of light in nonlinear materials is here studied in the regime of
the geometrical optics. It is shown that a spherically symmetric medium at rest
with some specific dielectric properties can be used to produce an exact
analogue model for a class of space-times which includes spherically symmetric
and static black hole solutions. The optical model here presented can be a
useful tool to reproduce in laboratory the behavior of optical null geodesics
near a compact object with an observable gravitational Schwarzschild radius.
| [
{
"created": "Tue, 28 Jan 2014 09:50:37 GMT",
"version": "v1"
}
] | 2015-02-17 | [
[
"Bittencourt",
"E.",
""
],
[
"De Lorenci",
"V. A.",
""
],
[
"Klippert",
"R.",
""
],
[
"Novello",
"M.",
""
],
[
"Salim",
"J. M.",
""
]
] | Propagation of light in nonlinear materials is here studied in the regime of the geometrical optics. It is shown that a spherically symmetric medium at rest with some specific dielectric properties can be used to produce an exact analogue model for a class of space-times which includes spherically symmetric and static black hole solutions. The optical model here presented can be a useful tool to reproduce in laboratory the behavior of optical null geodesics near a compact object with an observable gravitational Schwarzschild radius. |
1506.04164 | Babak Vakili | V. Hosseinzadeh, M. A. Gorji, K. Nozari and B. Vakili | Noncommutative spaces and covariant formulation of statistical mechanics | 12 two column pages, 2 figures, Final version | Phys. Rev. D 92 (2015) 025008 | 10.1103/PhysRevD.92.025008 | null | gr-qc cond-mat.stat-mech hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the statistical mechanics of a general Hamiltonian system in the
context of symplectic structure of the corresponding phase space. This
covariant formalism reveals some interesting correspondences between properties
of the phase space and the associated statistical physics. While topology, as a
global property, turns out to be related to the total number of microstates,
the invariant measure which assigns {\it a priori} probability distribution
over the microstates, is determined by the local form of the symplectic
structure. As an example of a model for which the phase space has a nontrivial
topology, we apply our formulation on the Snyder noncommutative space-time with
de Sitter four-momentum space and analyze the results. Finally, in the
framework of such a setup, we examine our formalism by studying the
thermodynamical properties of a harmonic oscillator system.
| [
{
"created": "Fri, 12 Jun 2015 20:14:33 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Jul 2015 10:10:57 GMT",
"version": "v2"
}
] | 2015-07-10 | [
[
"Hosseinzadeh",
"V.",
""
],
[
"Gorji",
"M. A.",
""
],
[
"Nozari",
"K.",
""
],
[
"Vakili",
"B.",
""
]
] | We study the statistical mechanics of a general Hamiltonian system in the context of symplectic structure of the corresponding phase space. This covariant formalism reveals some interesting correspondences between properties of the phase space and the associated statistical physics. While topology, as a global property, turns out to be related to the total number of microstates, the invariant measure which assigns {\it a priori} probability distribution over the microstates, is determined by the local form of the symplectic structure. As an example of a model for which the phase space has a nontrivial topology, we apply our formulation on the Snyder noncommutative space-time with de Sitter four-momentum space and analyze the results. Finally, in the framework of such a setup, we examine our formalism by studying the thermodynamical properties of a harmonic oscillator system. |
0707.4665 | Peter K.F. Kuhfittig | Peter K. F. Kuhfittig | Wormholes with a space- and time-dependent equation of state | 6 pages RevTeX 4 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The discovery that the Universe is undergoing an accelerated expansion has
suggested the existence of an evolving equation of state. This paper discusses
various wormhole solutions in a spherically symmetric spacetime with an
equation of state that is both space and time dependent. The solutions obtained
are exact and generalize earlier results on static wormholes supported by
phantom energy.
| [
{
"created": "Tue, 31 Jul 2007 18:01:22 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Mar 2011 17:27:09 GMT",
"version": "v2"
}
] | 2011-03-15 | [
[
"Kuhfittig",
"Peter K. F.",
""
]
] | The discovery that the Universe is undergoing an accelerated expansion has suggested the existence of an evolving equation of state. This paper discusses various wormhole solutions in a spherically symmetric spacetime with an equation of state that is both space and time dependent. The solutions obtained are exact and generalize earlier results on static wormholes supported by phantom energy. |
1006.1294 | Carlo Rovelli | You Ding, Carlo Rovelli | Physical boundary Hilbert space and volume operator in the Lorentzian
new spin-foam theory | 11 pages | Class.Quant.Grav.27:205003,2010 | 10.1088/0264-9381/27/20/205003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A covariant spin-foam formulation of quantum gravity has been recently
developed, characterized by a kinematics which appears to match well the one of
canonical loop quantum gravity. In this paper we reconsider the implementation
of the constraints that defines the model. We define in a simple way the
boundary Hilbert space of the theory, introducing a slight modification of the
embedding of the SU(2) representations into the SL(2,C) ones. We then show
directly that all constraints vanish on this space in a weak sense. The
vanishing is exact (and not just in the large quantum number limit.) We also
generalize the definition of the volume operator in the spinfoam model to the
Lorentzian signature, and show that it matches the one of loop quantum gravity,
as does in the Euclidean case.
| [
{
"created": "Mon, 7 Jun 2010 16:41:29 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Jun 2010 15:07:04 GMT",
"version": "v2"
},
{
"created": "Thu, 10 Jun 2010 16:16:24 GMT",
"version": "v3"
}
] | 2014-11-21 | [
[
"Ding",
"You",
""
],
[
"Rovelli",
"Carlo",
""
]
] | A covariant spin-foam formulation of quantum gravity has been recently developed, characterized by a kinematics which appears to match well the one of canonical loop quantum gravity. In this paper we reconsider the implementation of the constraints that defines the model. We define in a simple way the boundary Hilbert space of the theory, introducing a slight modification of the embedding of the SU(2) representations into the SL(2,C) ones. We then show directly that all constraints vanish on this space in a weak sense. The vanishing is exact (and not just in the large quantum number limit.) We also generalize the definition of the volume operator in the spinfoam model to the Lorentzian signature, and show that it matches the one of loop quantum gravity, as does in the Euclidean case. |
2105.13983 | Do\u{g}a Veske | Do\u{g}a Veske, Imre Bartos, Zsuzsa M\'arka, Szabolcs M\'arka | Characterizing the observation bias in gravitational-wave detections and
finding structured population properties | Accepted to ApJ. 8 pages, 3 figures + 2 page appendix | null | 10.3847/1538-4357/ac27ac | null | gr-qc astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The observed distributions of the source properties from gravitational-wave
detections are biased due to the selection effects and detection criteria in
the detections, analogous to the Malmquist bias. In this work, this observation
bias is investigated through its fundamental statistical and physical origins.
An efficient semi-analytical formulation for its estimation is derived which is
as accurate as the standard method of numerical simulations, with only a
millionth of the computational cost. Then, the estimated bias is used for
unmodelled inferences on the binary black hole population. These inferences
show additional structures, specifically two peaks in the joint mass
distribution around binary masses $\sim10$ M$_\odot$ and $\sim30$ M$_\odot$.
Example ready-to-use scripts and some produced datasets for this method are
shared in an online repository.
| [
{
"created": "Fri, 28 May 2021 17:08:04 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Oct 2021 17:09:19 GMT",
"version": "v2"
}
] | 2021-12-15 | [
[
"Veske",
"Doğa",
""
],
[
"Bartos",
"Imre",
""
],
[
"Márka",
"Zsuzsa",
""
],
[
"Márka",
"Szabolcs",
""
]
] | The observed distributions of the source properties from gravitational-wave detections are biased due to the selection effects and detection criteria in the detections, analogous to the Malmquist bias. In this work, this observation bias is investigated through its fundamental statistical and physical origins. An efficient semi-analytical formulation for its estimation is derived which is as accurate as the standard method of numerical simulations, with only a millionth of the computational cost. Then, the estimated bias is used for unmodelled inferences on the binary black hole population. These inferences show additional structures, specifically two peaks in the joint mass distribution around binary masses $\sim10$ M$_\odot$ and $\sim30$ M$_\odot$. Example ready-to-use scripts and some produced datasets for this method are shared in an online repository. |
gr-qc/0701052 | Daniel Alonso | Daniel Alonso, Antonia Ruiz and Manuel S\'anchez-Hern\'andez | Escape of photons from two fixed extreme Reissner-Nordstr\"om black
holes | Final version | Phys.Rev.D78:104024,2008 | 10.1103/PhysRevD.78.104024 | null | gr-qc nlin.CD | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the scattering of light (null geodesics) by two fixed extreme
Reissner-Nordstr\"om black holes, in which the gravitational attraction of
their masses is exactly balanced with the electrostatic repulsion of their
charges, allowing a static spacetime. We identify the set of unstable periodic
orbits that constitute the fractal repeller that completely describes the
chaotic escape dynamics of photons. In the framework of periodic orbit theory,
the analysis of the linear stability of the unstable periodic orbits is used to
obtain the main quantities of chaos that characterize the escape dynamics of
the photons scattered by the black holes. In particular, the escape rate which
is compared with the result obtained from numerical simulations that consider
statistical ensembles of photons. We also analyze the dynamics of photons in
the proximity of a perturbed black hole and give an analytical estimation for
the escape rate in this system.
| [
{
"created": "Tue, 9 Jan 2007 15:57:37 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Nov 2008 12:11:29 GMT",
"version": "v2"
}
] | 2009-02-23 | [
[
"Alonso",
"Daniel",
""
],
[
"Ruiz",
"Antonia",
""
],
[
"Sánchez-Hernández",
"Manuel",
""
]
] | We study the scattering of light (null geodesics) by two fixed extreme Reissner-Nordstr\"om black holes, in which the gravitational attraction of their masses is exactly balanced with the electrostatic repulsion of their charges, allowing a static spacetime. We identify the set of unstable periodic orbits that constitute the fractal repeller that completely describes the chaotic escape dynamics of photons. In the framework of periodic orbit theory, the analysis of the linear stability of the unstable periodic orbits is used to obtain the main quantities of chaos that characterize the escape dynamics of the photons scattered by the black holes. In particular, the escape rate which is compared with the result obtained from numerical simulations that consider statistical ensembles of photons. We also analyze the dynamics of photons in the proximity of a perturbed black hole and give an analytical estimation for the escape rate in this system. |
1612.08222 | Krzysztof Bolejko | Krzysztof Bolejko, and Miko{\l}aj Korzy\'nski | Inhomogeneous cosmology and backreaction: Current status and future
prospects | A review article that includes a survey of 50 academics and their
opinions; 24 pages and 3 figures with survey results; v3 - matches published
version | Int. J. Mod. Phys. D 26, 1730011 (2017) | 10.1142/S0218271817300117 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Astronomical observations reveal hierarchical structures in the Universe,
from galaxies, groups of galaxies, clusters and superclusters, to filaments and
voids. On the largest scales it seems that some kind of statistical homogeneity
can be observed. As a result, modern cosmological models are based on spatially
homogeneous and isotropic solutions of the Einstein equations, and the
evolution of the universe is approximated by the Friedmann equations. In
parallel to standard homogeneous cosmology, the field of inhomogeneous
cosmology and backreaction is being developed. This field investigates whether
small scale inhomogeneities via non-linear effects can backreact and alter the
properties of the Universe on its largest scales, leading to a non-Friedmannian
evolution. This paper presents the current status of inhomogeneous cosmology
and backreaction. It also discusses future prospects of the field of
inhomogeneous cosmology, which is based on a survey of 50 academics working in
the field of inhomogeneous cosmology.
| [
{
"created": "Sat, 24 Dec 2016 22:16:18 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Jan 2017 23:01:08 GMT",
"version": "v2"
},
{
"created": "Mon, 22 May 2017 13:36:44 GMT",
"version": "v3"
}
] | 2017-05-23 | [
[
"Bolejko",
"Krzysztof",
""
],
[
"Korzyński",
"Mikołaj",
""
]
] | Astronomical observations reveal hierarchical structures in the Universe, from galaxies, groups of galaxies, clusters and superclusters, to filaments and voids. On the largest scales it seems that some kind of statistical homogeneity can be observed. As a result, modern cosmological models are based on spatially homogeneous and isotropic solutions of the Einstein equations, and the evolution of the universe is approximated by the Friedmann equations. In parallel to standard homogeneous cosmology, the field of inhomogeneous cosmology and backreaction is being developed. This field investigates whether small scale inhomogeneities via non-linear effects can backreact and alter the properties of the Universe on its largest scales, leading to a non-Friedmannian evolution. This paper presents the current status of inhomogeneous cosmology and backreaction. It also discusses future prospects of the field of inhomogeneous cosmology, which is based on a survey of 50 academics working in the field of inhomogeneous cosmology. |
1507.07314 | Chandra Prakash Singh | C. P. Singh and Pankaj Kumar | Holographic dark energy models with statefinder diagnostic in modified
$f(R,T)$ gravity | 12 pages, 4 figures, MS has been revised | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study non-viscous and viscous holographic dark energy models for a
homogeneous and isotropic flat Friedmann-Robertson-Walker Universe in $f(R,T)$
gravity. We find that the Hubble horizon as an IR cut-off is suitable for both
the models to explain the recent accelerated expansion of the Universe. The
cosmological parameters like deceleration parameter and statefinder parameters
are discussed in each model. In non-viscous model a constant deceleration
parameter is found which shows that there is no phase transition. The
constraints on the parameters are obtained to analyse the fixed point values of
statefinder parameters of SCDM and $\Lambda$CDM models. We know that the phase
transition is required to explain the accelerated expansion of the Universe and
this is possible if both the parameters would be time-dependent. Therefore, we
extend our analysis to viscous holographic dark energy model to investigate
whether this viscous model with the same IR cut-off could be helpful to find
the phase transition. We find that this model gives a time-dependent
deceleration parameter which achieves a smooth phase transition of the
Universe. We also find the time-varying statefinder pair which matches with
$\Lambda$CDM model. We plot the trajectories in $r-s$ and $r-q$ plans to
discriminate our model with the existing dark energy models and obtain the
quintessence like behaviour for the suitable values of parameters.
| [
{
"created": "Mon, 27 Jul 2015 06:55:22 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Oct 2015 06:51:22 GMT",
"version": "v2"
}
] | 2015-10-15 | [
[
"Singh",
"C. P.",
""
],
[
"Kumar",
"Pankaj",
""
]
] | We study non-viscous and viscous holographic dark energy models for a homogeneous and isotropic flat Friedmann-Robertson-Walker Universe in $f(R,T)$ gravity. We find that the Hubble horizon as an IR cut-off is suitable for both the models to explain the recent accelerated expansion of the Universe. The cosmological parameters like deceleration parameter and statefinder parameters are discussed in each model. In non-viscous model a constant deceleration parameter is found which shows that there is no phase transition. The constraints on the parameters are obtained to analyse the fixed point values of statefinder parameters of SCDM and $\Lambda$CDM models. We know that the phase transition is required to explain the accelerated expansion of the Universe and this is possible if both the parameters would be time-dependent. Therefore, we extend our analysis to viscous holographic dark energy model to investigate whether this viscous model with the same IR cut-off could be helpful to find the phase transition. We find that this model gives a time-dependent deceleration parameter which achieves a smooth phase transition of the Universe. We also find the time-varying statefinder pair which matches with $\Lambda$CDM model. We plot the trajectories in $r-s$ and $r-q$ plans to discriminate our model with the existing dark energy models and obtain the quintessence like behaviour for the suitable values of parameters. |
1503.07060 | Oleg Tsupko | Paul I. Jefremov, Oleg Yu. Tsupko, and Gennady S. Bisnovatyi-Kogan | Innermost stable circular orbits of spinning test particles in
Schwarzschild and Kerr space-times | accepted to PhysRevD, 15 pages, 5 figures | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the motion of classical spinning test particles in Schwarzschild
and Kerr metrics and investigate innermost stable circular orbits (ISCO). The
main goal of this work is to find analytically the small-spin corrections for
the parameters of ISCO (radius, total angular momentum, energy, orbital angular
frequency) of spinning test particles in the case of vectors of black hole
spin, particle spin and orbital angular momentum being collinear to each other.
We analytically derive the small-spin linear corrections for arbitrary Kerr
parameter $a$. The cases of Schwarzschild, slowly rotating and extreme Kerr
black hole are considered in details. For a slowly rotating black hole the ISCO
parameters are obtained up to quadratic in $a$ and particle's spin $s$ terms.
From the formulae obtained it is seen that the spin-orbital coupling has
attractive character when spin and angular momentum are parallel and repulsive
when they are antiparallel. For the case of the extreme Kerr black hole with
co-rotating particle we succeed to find the exact analytical solution for the
limiting ISCO parameters for arbitrary spin. It has been shown that the
limiting values of ISCO radius and frequency do not depend on the particle's
spin while values of energy and total angular momentum depend on it. We have
also considered circular orbits of arbitrary radius and have found small-spin
linear corrections for the total angular momentum and energy at given radius.
System of equations for numerical calculation of ISCO parameters for arbitrary
$a$ and $s$ is also explicitly written.
| [
{
"created": "Tue, 24 Mar 2015 14:38:29 GMT",
"version": "v1"
},
{
"created": "Fri, 22 May 2015 09:29:41 GMT",
"version": "v2"
}
] | 2015-05-25 | [
[
"Jefremov",
"Paul I.",
""
],
[
"Tsupko",
"Oleg Yu.",
""
],
[
"Bisnovatyi-Kogan",
"Gennady S.",
""
]
] | We consider the motion of classical spinning test particles in Schwarzschild and Kerr metrics and investigate innermost stable circular orbits (ISCO). The main goal of this work is to find analytically the small-spin corrections for the parameters of ISCO (radius, total angular momentum, energy, orbital angular frequency) of spinning test particles in the case of vectors of black hole spin, particle spin and orbital angular momentum being collinear to each other. We analytically derive the small-spin linear corrections for arbitrary Kerr parameter $a$. The cases of Schwarzschild, slowly rotating and extreme Kerr black hole are considered in details. For a slowly rotating black hole the ISCO parameters are obtained up to quadratic in $a$ and particle's spin $s$ terms. From the formulae obtained it is seen that the spin-orbital coupling has attractive character when spin and angular momentum are parallel and repulsive when they are antiparallel. For the case of the extreme Kerr black hole with co-rotating particle we succeed to find the exact analytical solution for the limiting ISCO parameters for arbitrary spin. It has been shown that the limiting values of ISCO radius and frequency do not depend on the particle's spin while values of energy and total angular momentum depend on it. We have also considered circular orbits of arbitrary radius and have found small-spin linear corrections for the total angular momentum and energy at given radius. System of equations for numerical calculation of ISCO parameters for arbitrary $a$ and $s$ is also explicitly written. |
0804.1036 | Andreas Freise | A. Freise, S. Chelkowski, S. Hild, W. Del Pozzo, A. Perreca and A.
Vecchio | Triple Michelson Interferometer for a Third-Generation Gravitational
Wave Detector | Minor corrections to the main text and two additional appendices. 14
pages, 6 figures | null | 10.1088/0264-9381/26/8/085012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The upcoming European design study `Einstein gravitational-wave Telescope'
represents the first step towards a substantial, international effort for the
design of a third-generation interferometric gravitational wave detector. It is
generally believed that third-generation instruments might not be installed
into existing infrastructures but will provoke a new search for optimal
detector sites. Consequently, the detector design could be subject to fewer
constraints than the on-going design of the second generation instruments. In
particular, it will be prudent to investigate alternatives to the traditional
L-shaped Michelson interferometer. In this article, we review an old proposal
to use three Michelson interferometers in a triangular configuration. We use
this example of a triple Michelson interferometer to clarify the terminology
and will put this idea into the context of more recent research on
interferometer technologies. Furthermore the benefits of a triangular detector
will be used to motivate this design as a good starting point for a more
detailed research effort towards a third-generation gravitational wave
detector.
| [
{
"created": "Mon, 7 Apr 2008 14:22:54 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Mar 2009 05:23:20 GMT",
"version": "v2"
}
] | 2009-11-13 | [
[
"Freise",
"A.",
""
],
[
"Chelkowski",
"S.",
""
],
[
"Hild",
"S.",
""
],
[
"Del Pozzo",
"W.",
""
],
[
"Perreca",
"A.",
""
],
[
"Vecchio",
"A.",
""
]
] | The upcoming European design study `Einstein gravitational-wave Telescope' represents the first step towards a substantial, international effort for the design of a third-generation interferometric gravitational wave detector. It is generally believed that third-generation instruments might not be installed into existing infrastructures but will provoke a new search for optimal detector sites. Consequently, the detector design could be subject to fewer constraints than the on-going design of the second generation instruments. In particular, it will be prudent to investigate alternatives to the traditional L-shaped Michelson interferometer. In this article, we review an old proposal to use three Michelson interferometers in a triangular configuration. We use this example of a triple Michelson interferometer to clarify the terminology and will put this idea into the context of more recent research on interferometer technologies. Furthermore the benefits of a triangular detector will be used to motivate this design as a good starting point for a more detailed research effort towards a third-generation gravitational wave detector. |
1208.3184 | Mahmood Roshan | Mahmood Roshan | Parametrized post-Newtonian virial theorem | 10 pages, submitted to CQG | Class. Quantum Grav. 29 (2012) 215001 | 10.1088/0264-9381/29/21/215001 | IPM-P-2012-037 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the parametrized post-Newtonian equations of hydrodynamics, we derive
the tensor form of the parametrized post-Newtonian virial theorem.
| [
{
"created": "Wed, 15 Aug 2012 19:30:35 GMT",
"version": "v1"
}
] | 2012-10-16 | [
[
"Roshan",
"Mahmood",
""
]
] | Using the parametrized post-Newtonian equations of hydrodynamics, we derive the tensor form of the parametrized post-Newtonian virial theorem. |
2010.13495 | Alireza Talebian Ashkezari | Seyed Ali Hosseini Mansoori, Alireza Talebian and Hassan Firouzjahi | Mimetic Inflation | 19+9 pages, 29 figures, 2 appendices. Accepted by JHEP | null | 10.1007/JHEP01(2021)183 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study inflationary solution in an extension of mimetic gravity with the
higher derivative interactions coupled to gravity. Because of the higher
derivative interactions, the setup is free from the ghost and gradient
instabilities while it hosts a number of novel properties. The dispersion
relation of scalar perturbations develops quartic momentum correction similar
to the setup of ghost inflation. Furthermore, the tilt of tensor perturbations
can take either signs with a modified consistency relation between the tilt and
the amplitude of tensor perturbations. Despite the presence of higher
derivative interactions coupled to gravity, the tensor perturbations propagate
with a speed equal to the speed of light as required by the LIGO observations.
Furthermore, the higher derivative interactions induce non-trivial interactions
in cubic Hamiltonian, generating non-Gaussianities in various shapes such as
the equilateral, orthogonal, and squeezed configurations with observable
amplitudes.
| [
{
"created": "Mon, 26 Oct 2020 11:36:10 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Oct 2020 11:43:03 GMT",
"version": "v2"
},
{
"created": "Thu, 24 Dec 2020 15:18:52 GMT",
"version": "v3"
}
] | 2021-02-24 | [
[
"Mansoori",
"Seyed Ali Hosseini",
""
],
[
"Talebian",
"Alireza",
""
],
[
"Firouzjahi",
"Hassan",
""
]
] | We study inflationary solution in an extension of mimetic gravity with the higher derivative interactions coupled to gravity. Because of the higher derivative interactions, the setup is free from the ghost and gradient instabilities while it hosts a number of novel properties. The dispersion relation of scalar perturbations develops quartic momentum correction similar to the setup of ghost inflation. Furthermore, the tilt of tensor perturbations can take either signs with a modified consistency relation between the tilt and the amplitude of tensor perturbations. Despite the presence of higher derivative interactions coupled to gravity, the tensor perturbations propagate with a speed equal to the speed of light as required by the LIGO observations. Furthermore, the higher derivative interactions induce non-trivial interactions in cubic Hamiltonian, generating non-Gaussianities in various shapes such as the equilateral, orthogonal, and squeezed configurations with observable amplitudes. |
1711.04167 | Ingrid Irmer | Ingrid Irmer | Examples of covering properties of boundary points of space-times | null | null | 10.1142/S021988781850192X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The problem of classifying boundary points of space-time, for example
singularities, regular points and points at infinity, is an unexpectedly subtle
one. Due to the fact that whether or not two boundary points are identified or
even "nearby" is dependant on the way the space-time is embedded, difficulties
occur when singularities are thought of as an inherently local aspect of a
space-time, as an analogy with electromagnetism would imply. The completion of
a manifold with respect to a pseudo-Riemannian metric can be defined
intrinsically, [SS94]. This is done via an equivalence relation, formalising
which boundary sets cover other sets. This paper works through the
possibilities, providing examples to show that all covering relations not
immediately ruled out by the definitions are possible.
| [
{
"created": "Sat, 11 Nov 2017 16:38:38 GMT",
"version": "v1"
}
] | 2018-11-14 | [
[
"Irmer",
"Ingrid",
""
]
] | The problem of classifying boundary points of space-time, for example singularities, regular points and points at infinity, is an unexpectedly subtle one. Due to the fact that whether or not two boundary points are identified or even "nearby" is dependant on the way the space-time is embedded, difficulties occur when singularities are thought of as an inherently local aspect of a space-time, as an analogy with electromagnetism would imply. The completion of a manifold with respect to a pseudo-Riemannian metric can be defined intrinsically, [SS94]. This is done via an equivalence relation, formalising which boundary sets cover other sets. This paper works through the possibilities, providing examples to show that all covering relations not immediately ruled out by the definitions are possible. |
1609.06398 | F. S. Guzman | M. Gracia-Linares and F. S. Guzman | Accretion of Supersonic Winds on Boson Stars | 8 pages, 10 pdf figures. Accepted for publication in Physical Review
D | Phys. Rev. D 94, 064077 (2016) | 10.1103/PhysRevD.94.064077 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the evolution of a supersonic wind interacting with a Boson Star
(BS) and compare the resulting wind density profile with that of the shock cone
formed when the wind is accreted by a non-rotating Black Hole (BH) of the same
mass. The physical differences between these accretors are that a BS, unlike a
BH has no horizon, it does not have a mechanical surface either and thus the
wind is expected to trespass the BS. Despite these conditions, on the BS
space-time the gas achieves a stationary flux with the gas accumulating in a
high density elongated structure comparable to the shock cone formed behind a
BH. The highest density resides in the center of the BS whereas in the case of
the BH it is found on the downstream part of the BH near the event horizon. The
maximum density of the gas is smaller in the BS than in the BH case. Our
results indicate that the highest density of the wind is more similar on the BS
to that on the BH when the BS has high self-interaction, when it is more
compact and when the wind velocity is higher. We expect this and similar
analyses help to know whether BSs can still be Black Hole mimickers or can be
ruled out.
| [
{
"created": "Wed, 21 Sep 2016 01:43:05 GMT",
"version": "v1"
}
] | 2016-10-14 | [
[
"Gracia-Linares",
"M.",
""
],
[
"Guzman",
"F. S.",
""
]
] | We present the evolution of a supersonic wind interacting with a Boson Star (BS) and compare the resulting wind density profile with that of the shock cone formed when the wind is accreted by a non-rotating Black Hole (BH) of the same mass. The physical differences between these accretors are that a BS, unlike a BH has no horizon, it does not have a mechanical surface either and thus the wind is expected to trespass the BS. Despite these conditions, on the BS space-time the gas achieves a stationary flux with the gas accumulating in a high density elongated structure comparable to the shock cone formed behind a BH. The highest density resides in the center of the BS whereas in the case of the BH it is found on the downstream part of the BH near the event horizon. The maximum density of the gas is smaller in the BS than in the BH case. Our results indicate that the highest density of the wind is more similar on the BS to that on the BH when the BS has high self-interaction, when it is more compact and when the wind velocity is higher. We expect this and similar analyses help to know whether BSs can still be Black Hole mimickers or can be ruled out. |
1212.3417 | Salvador Robles-Perez | S. J. Robles-P\'erez and P. F. Gonz\'alez-D\'iaz | Inter-universal quantum entanglement | 3 pages, no figure. Prepared for the proceedings of the "Thirteenth
Marcel Grossmann Meeting" | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The boundary conditions to be imposed on the quantum state of the whole
multiverse could be such that the universes would be created in entangled
pairs. Then, inter-universal entanglement would provide us with a vacuum energy
for each single universe that might be fitted with observational data, making
testable not only the multiverse proposal but also the boundary conditions of
the multiverse. Furthermore, the second law of the entanglement thermodynamics
would enhance the expansion of the single universes.
| [
{
"created": "Fri, 14 Dec 2012 09:15:01 GMT",
"version": "v1"
}
] | 2012-12-17 | [
[
"Robles-Pérez",
"S. J.",
""
],
[
"González-Díaz",
"P. F.",
""
]
] | The boundary conditions to be imposed on the quantum state of the whole multiverse could be such that the universes would be created in entangled pairs. Then, inter-universal entanglement would provide us with a vacuum energy for each single universe that might be fitted with observational data, making testable not only the multiverse proposal but also the boundary conditions of the multiverse. Furthermore, the second law of the entanglement thermodynamics would enhance the expansion of the single universes. |
2403.08250 | Camilo Posada PhD | Philip Beltracchi and Camilo Posada | Slowly rotating anisotropic relativistic stars | 27 pages, 30 figures. Discussion in Appendix B extended. Matches the
published version in PRD | Phys. Rev. D 110, 024052 (2024) | 10.1103/PhysRevD.110.024052 | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present paper is devoted to a study of the equilibrium configurations of
slowly rotating anisotropic stars in the framework of general relativity. For
that purpose, we provide the equations of structure where the rotation is
treated to second order in the angular velocity. These equations extend those
first derived by Hartle for slowly rotating isotropic stars. As an application
of the new formalism, we study the rotational properties of Bowers-Liang fluid
spheres. A result of particular interest is that the ellipticity and mass
quadrupole moment are negative for certain highly anisotropic configurations;
thus, such systems are prolate rather than oblate. Furthermore, for
configurations with high anisotropy and compactness close to their critical
value, quantities like the moment of inertia, change of mass, and mass
quadrupole moment approach to the corresponding Kerr black hole values, similar
to other ultracompact systems like sub-Buchdahl Schwarzschild stars and
analytic rotating gravastars.
| [
{
"created": "Wed, 13 Mar 2024 05:07:01 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Jul 2024 15:55:43 GMT",
"version": "v2"
}
] | 2024-07-23 | [
[
"Beltracchi",
"Philip",
""
],
[
"Posada",
"Camilo",
""
]
] | The present paper is devoted to a study of the equilibrium configurations of slowly rotating anisotropic stars in the framework of general relativity. For that purpose, we provide the equations of structure where the rotation is treated to second order in the angular velocity. These equations extend those first derived by Hartle for slowly rotating isotropic stars. As an application of the new formalism, we study the rotational properties of Bowers-Liang fluid spheres. A result of particular interest is that the ellipticity and mass quadrupole moment are negative for certain highly anisotropic configurations; thus, such systems are prolate rather than oblate. Furthermore, for configurations with high anisotropy and compactness close to their critical value, quantities like the moment of inertia, change of mass, and mass quadrupole moment approach to the corresponding Kerr black hole values, similar to other ultracompact systems like sub-Buchdahl Schwarzschild stars and analytic rotating gravastars. |
2010.14578 | Lu\'is Felipe Longo Micchi Mr. | Luis Felipe Longo Micchi, Niayesh Afshordi, Cecilia Chirenti | How loud are echoes from exotic compact objects? | 15 pages, 9 figures, minor changes, accepted for publication in PRD | Phys. Rev. D 103, 044028 (2021) | 10.1103/PhysRevD.103.044028 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The first direct observations of gravitational waves (GWs) by the LIGO
collaboration have motivated different tests of General Relativity (GR),
including the search for extra pulses following the GR waveform for the
coalescence of compact objects. The motivation for these searches comes from
the alternative proposal that the final compact object could differ from a
black hole (BH) by the lack of an event horizon and a central singularity. Such
objects are expected in theories that, motivated by quantum gravity
modifications, predict horizonless objects as the final stage of gravitational
collapse. In such a hypothetical case, this exotic compact object (ECO) will
present a (partially) reflective surface at $r_{\rm ECO}=r_{+}(1+\epsilon)$,
instead of an event horizon at $r_{+}$. For this class of objects, an
in-falling wave will not be completely lost and will give rise to secondary
pulses, to which recent literature refers as echoes. However, the largely
unknown ECO reflectivity is determinant for the amplitude of the signal, and
details also depend on the initial conditions of the progenitor compact binary.
Here, for the first time, we obtain estimates for the detectability of the
first echo, using a perturbative description for the inspiral-merger-ringdown
waveform and a physically-motivated ECO reflectivity. Binaries with comparable
masses will have a stronger first echo, improving the chances of detection. For
a case like GW150914, the detection of the first echo will require a minimum
ringdown signal-to-noise ratio (SNR) in the range $\sim 20-60$. The most
optimistic scenario for echo detection could already be probed by LIGO in the
next years. With the expected improvements in sensitivity we estimate one or
two events per year to have the required SNR for the first echo detection
during O4.
| [
{
"created": "Tue, 27 Oct 2020 19:40:43 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jan 2021 18:38:36 GMT",
"version": "v2"
}
] | 2021-02-22 | [
[
"Micchi",
"Luis Felipe Longo",
""
],
[
"Afshordi",
"Niayesh",
""
],
[
"Chirenti",
"Cecilia",
""
]
] | The first direct observations of gravitational waves (GWs) by the LIGO collaboration have motivated different tests of General Relativity (GR), including the search for extra pulses following the GR waveform for the coalescence of compact objects. The motivation for these searches comes from the alternative proposal that the final compact object could differ from a black hole (BH) by the lack of an event horizon and a central singularity. Such objects are expected in theories that, motivated by quantum gravity modifications, predict horizonless objects as the final stage of gravitational collapse. In such a hypothetical case, this exotic compact object (ECO) will present a (partially) reflective surface at $r_{\rm ECO}=r_{+}(1+\epsilon)$, instead of an event horizon at $r_{+}$. For this class of objects, an in-falling wave will not be completely lost and will give rise to secondary pulses, to which recent literature refers as echoes. However, the largely unknown ECO reflectivity is determinant for the amplitude of the signal, and details also depend on the initial conditions of the progenitor compact binary. Here, for the first time, we obtain estimates for the detectability of the first echo, using a perturbative description for the inspiral-merger-ringdown waveform and a physically-motivated ECO reflectivity. Binaries with comparable masses will have a stronger first echo, improving the chances of detection. For a case like GW150914, the detection of the first echo will require a minimum ringdown signal-to-noise ratio (SNR) in the range $\sim 20-60$. The most optimistic scenario for echo detection could already be probed by LIGO in the next years. With the expected improvements in sensitivity we estimate one or two events per year to have the required SNR for the first echo detection during O4. |
1506.08699 | M. Farasat Shamir | M. Farasat Shamir | Bianchi Type $I$ Cosmology in $f(R,T)$ Gravity | 17 Pages, Extended analysis of arXiv:1207.0708 | J. Exp. Theor. Phys. 119(2): 242-250, 2014 | 10.1134/S1063776114070073 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper is devoted to investigate the exact solutions of Bianchi type $I$
spacetime in the context of $f(R,T)$ gravity [1], where $f(R,T)$ is an
arbitrary function of Ricci scalar $R$ and trace of the energy momentum tensor
$T$. For this purpose, we find two exact solutions using the assumption of
constant deceleration parameter and variation law of Hubble parameter. The
obtained solutions correspond to two different models of the universe. The
physical behaviour of these models is also discussed.
| [
{
"created": "Fri, 26 Jun 2015 19:12:56 GMT",
"version": "v1"
}
] | 2015-06-30 | [
[
"Shamir",
"M. Farasat",
""
]
] | This paper is devoted to investigate the exact solutions of Bianchi type $I$ spacetime in the context of $f(R,T)$ gravity [1], where $f(R,T)$ is an arbitrary function of Ricci scalar $R$ and trace of the energy momentum tensor $T$. For this purpose, we find two exact solutions using the assumption of constant deceleration parameter and variation law of Hubble parameter. The obtained solutions correspond to two different models of the universe. The physical behaviour of these models is also discussed. |
1508.06457 | Dennis Philipp | Dennis Philipp, Volker Perlick, Claus Laemmerzahl, Kaustubh Deshpande | On geodesic deviation in Schwarzschild spacetime | 6 pages, 3 figures, contribution to conference on Metrology for
Aerospace 2015 - relativistic metrology session | Metrology for Aerospace (MetroAeroSpace), 2015 IEEE, pp.198-203 | 10.1109/MetroAeroSpace.2015.7180653 | null | gr-qc astro-ph.EP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For metrology, geodesy and gravimetry in space, satellite based instruments
and measurement techniques are used and the orbits of the satellites as well as
possible deviations between nearby ones are of central interest. The
measurement of this deviation itself gives insight into the underlying
structure of the spacetime geometry, which is curved and therefore described by
the theory of general relativity (GR). In the context of GR, the deviation of
nearby geodesics can be described by the Jacobi equation that is a result of
linearizing the geodesic equation around a known reference geodesic with
respect to the deviation vector and the relative velocity. We review the
derivation of this Jacobi equation and restrict ourselves to the simple case of
the spacetime outside a spherically symmetric mass distribution and circular
reference geodesics to find solutions by projecting the Jacobi equation on a
parallel propagated tetrad as done by Fuchs. Using his results, we construct
solutions of the Jacobi equation for different physical initial scenarios
inspired by satellite gravimetry missions and give a set of parameter together
with their precise impact on satellite orbit deviation. We further consider the
Newtonian analog and construct the full solution, that exhibits a similar
structure, within this theory.
| [
{
"created": "Wed, 26 Aug 2015 12:06:51 GMT",
"version": "v1"
}
] | 2015-08-27 | [
[
"Philipp",
"Dennis",
""
],
[
"Perlick",
"Volker",
""
],
[
"Laemmerzahl",
"Claus",
""
],
[
"Deshpande",
"Kaustubh",
""
]
] | For metrology, geodesy and gravimetry in space, satellite based instruments and measurement techniques are used and the orbits of the satellites as well as possible deviations between nearby ones are of central interest. The measurement of this deviation itself gives insight into the underlying structure of the spacetime geometry, which is curved and therefore described by the theory of general relativity (GR). In the context of GR, the deviation of nearby geodesics can be described by the Jacobi equation that is a result of linearizing the geodesic equation around a known reference geodesic with respect to the deviation vector and the relative velocity. We review the derivation of this Jacobi equation and restrict ourselves to the simple case of the spacetime outside a spherically symmetric mass distribution and circular reference geodesics to find solutions by projecting the Jacobi equation on a parallel propagated tetrad as done by Fuchs. Using his results, we construct solutions of the Jacobi equation for different physical initial scenarios inspired by satellite gravimetry missions and give a set of parameter together with their precise impact on satellite orbit deviation. We further consider the Newtonian analog and construct the full solution, that exhibits a similar structure, within this theory. |
2111.01268 | Jibitesh Dutta | Wompherdeiki Khyllep, Jibitesh Dutta, Spyros Basilakos and Emmanuel N.
Saridakis | Background evolution and growth of structures in interacting dark energy
through dynamical system analysis | 13 pages, 5 figures, version to appear in Phys.Rev.D | Phys. Rev. D 105, 043511 (2022) | 10.1103/PhysRevD.105.043511 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply the formalism of dynamical system analysis to investigate the
evolution of interacting dark energy scenarios at the background and
perturbation levels in a unified way. Since the resulting dynamical system
contains the extra perturbation variable related to the matter overdensity, the
critical points of the background analysis split, corresponding to different
behavior of matter perturbations, and hence to stability properties. From the
combined analysis, we find critical points that describe the non-accelerating
matter-dominated epoch with the correct growth of matter structure, and the
fact that they are saddle provides the natural exit from this phase.
Furthermore, we find stable attractors at late times corresponding to a dark
energy-dominated accelerated solution with constant matter perturbations, as
required by observations. Thus, interacting cosmology can describe the matter
and dark energy epochs correctly, both at the background and perturbation
levels, which reveals the capabilities of the interaction.
| [
{
"created": "Mon, 1 Nov 2021 21:28:49 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Jan 2022 08:11:06 GMT",
"version": "v2"
}
] | 2022-02-10 | [
[
"Khyllep",
"Wompherdeiki",
""
],
[
"Dutta",
"Jibitesh",
""
],
[
"Basilakos",
"Spyros",
""
],
[
"Saridakis",
"Emmanuel N.",
""
]
] | We apply the formalism of dynamical system analysis to investigate the evolution of interacting dark energy scenarios at the background and perturbation levels in a unified way. Since the resulting dynamical system contains the extra perturbation variable related to the matter overdensity, the critical points of the background analysis split, corresponding to different behavior of matter perturbations, and hence to stability properties. From the combined analysis, we find critical points that describe the non-accelerating matter-dominated epoch with the correct growth of matter structure, and the fact that they are saddle provides the natural exit from this phase. Furthermore, we find stable attractors at late times corresponding to a dark energy-dominated accelerated solution with constant matter perturbations, as required by observations. Thus, interacting cosmology can describe the matter and dark energy epochs correctly, both at the background and perturbation levels, which reveals the capabilities of the interaction. |
2305.17942 | Tomohiro Kozuka | Shunichiro Kinoshita, Tomohiro Kozuka, Keiju Murata, Keita Sugawara | Quasinormal mode spectrum of the AdS black hole with the Robin boundary
condition | 24 pages, 10 figures. v2: published version, figures added | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the quasinormal mode (QNM) spectrum of an asymptotically AdS black
hole with the Robin boundary condition at infinity. We consider the
Schwarzshild-AdS$_4$ with the flat event horizon as the background spacetime
and study its scalar field perturbation. Denoting leading coefficients of slow-
and fast-decay modes of the scalar field at infinity as $\phi_1$ and $\phi_2$,
respectively, we assume a linear relation between them as $\phi_2 =
\cot(\theta/2) \phi_1$, where $\theta$ is a constant called the Robin parameter
and periodic under $\theta\sim\theta+2\pi$. In a certain range of the Robin
parameter, there is an instability driven by the boundary condition. We also
find the holonomy in the QNM spectrum under the parametric cycle of the
boundary condition: $\theta=0\to2\pi$. After the one-cycle, $n$-th overtone of
the QNM moves to $(n-1)$-th overtone. The fundamental tone of the QNM is swept
out to the infinity in the complex plane.
| [
{
"created": "Mon, 29 May 2023 08:05:55 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Feb 2024 05:44:13 GMT",
"version": "v2"
}
] | 2024-02-27 | [
[
"Kinoshita",
"Shunichiro",
""
],
[
"Kozuka",
"Tomohiro",
""
],
[
"Murata",
"Keiju",
""
],
[
"Sugawara",
"Keita",
""
]
] | We study the quasinormal mode (QNM) spectrum of an asymptotically AdS black hole with the Robin boundary condition at infinity. We consider the Schwarzshild-AdS$_4$ with the flat event horizon as the background spacetime and study its scalar field perturbation. Denoting leading coefficients of slow- and fast-decay modes of the scalar field at infinity as $\phi_1$ and $\phi_2$, respectively, we assume a linear relation between them as $\phi_2 = \cot(\theta/2) \phi_1$, where $\theta$ is a constant called the Robin parameter and periodic under $\theta\sim\theta+2\pi$. In a certain range of the Robin parameter, there is an instability driven by the boundary condition. We also find the holonomy in the QNM spectrum under the parametric cycle of the boundary condition: $\theta=0\to2\pi$. After the one-cycle, $n$-th overtone of the QNM moves to $(n-1)$-th overtone. The fundamental tone of the QNM is swept out to the infinity in the complex plane. |
1711.10890 | Martin Blaschke | Zden\v{e}k Stuchl\'ik, Martin Blaschke, Jan Schee | Particle collisions and optical effects in the mining Kerr--Newman
spacetimes | null | Phys. Rev. D 96, 104050, 28 November 2017 | 10.1103/PhysRevD.96.104050 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study ultra-high-energy particle collisions and optical effects in the
extraordinary class of mining braneworld Kerr-Newman (KN) naked singularity
spacetimes, predicting extremely high efficiency of Keplerian accretion, and
compare the results to those related to the other classes of the KN naked
singularity and black hole spacetimes. We demonstrate that in the mining KN
spacetimes the ultra-high centre-of-mass energy occurs for collisions of
particles following the extremely-low-energy stable circular geodesics of the
\uvozovky{mining regime}, colliding with large family of incoming particles,
e.g., those infalling from the marginally stable counter-rotating circular
geodesics. This is qualitatively different situation in comparison to the
standard KN naked singularity or black hole spacetimes where the collisional
ultra-high centre-of-mass energy can be obtained only in the near-extreme
spacetimes. We also show that observers following the stable circular geodesics
of the mining regime can register extremely blue-shifted radiation incoming
from the Universe, and see strongly deformed sky due to highly relativistic
motion along such stable orbits. The strongly blue-shifted radiation could be
thus a significant source of energy for such orbiting observers.
| [
{
"created": "Wed, 29 Nov 2017 14:52:33 GMT",
"version": "v1"
}
] | 2017-11-30 | [
[
"Stuchlík",
"Zdeněk",
""
],
[
"Blaschke",
"Martin",
""
],
[
"Schee",
"Jan",
""
]
] | We study ultra-high-energy particle collisions and optical effects in the extraordinary class of mining braneworld Kerr-Newman (KN) naked singularity spacetimes, predicting extremely high efficiency of Keplerian accretion, and compare the results to those related to the other classes of the KN naked singularity and black hole spacetimes. We demonstrate that in the mining KN spacetimes the ultra-high centre-of-mass energy occurs for collisions of particles following the extremely-low-energy stable circular geodesics of the \uvozovky{mining regime}, colliding with large family of incoming particles, e.g., those infalling from the marginally stable counter-rotating circular geodesics. This is qualitatively different situation in comparison to the standard KN naked singularity or black hole spacetimes where the collisional ultra-high centre-of-mass energy can be obtained only in the near-extreme spacetimes. We also show that observers following the stable circular geodesics of the mining regime can register extremely blue-shifted radiation incoming from the Universe, and see strongly deformed sky due to highly relativistic motion along such stable orbits. The strongly blue-shifted radiation could be thus a significant source of energy for such orbiting observers. |
2207.09034 | Matt Visser | Joshua Baines (Victoria University of Wellington) and Matt Visser
(Victoria University of Wellington) | Physically motivated ansatz for the Kerr spacetime | V1:19 pages; no figures. V2: one minor typo fixed; two new references | null | 10.1088/1361-6382/ac9bc5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Despite some 60 years of work on the subject of the Kerr rotating black hole
there is as yet no widely accepted physically based and pedagogically viable
ansatz suitable for deriving the Kerr solution without significant
computational effort. (Typically involving computer-aided symbolic algebra.)
Perhaps the closest one gets in this regard is the Newman-Janis trick; a trick
which requires several physically unmotivated choices in order to work. Herein
we shall try to make some progress on this issue by using a non-ortho-normal
tetrad based on oblate spheroidal coordinates to absorb as much of the messy
angular dependence as possible, leaving one to deal with a relatively simple
angle-independent tetrad-component metric. That is, we shall write $g_{ab} =
g_{AB} \; e^A{}_a\; e^B{}_b$ seeking to keep both the tetrad-component metric
$g_{AB}$ and the non-ortho-normal co-tetrad $e^A{}_a$ relatively simple but
non-trivial. We shall see that it is possible to put all the mass dependence
into $g_{AB}$, while the non-ortho-normal co-tetrad $e^A{}_a$ can be chosen to
be a mass-independent representation of flat Minkowski space in oblate
spheroidal coordinates: $(g_\mathrm{Minkowski})_{ab} = \eta_{AB} \; e^A{}_a\;
e^B{}_b$. This procedure separates out, to the greatest extent possible, the
mass dependence from the rotational dependence, and makes the Kerr solution
perhaps a little less mysterious.
| [
{
"created": "Tue, 19 Jul 2022 02:51:51 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Jul 2022 05:22:55 GMT",
"version": "v2"
}
] | 2022-11-23 | [
[
"Baines",
"Joshua",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | Despite some 60 years of work on the subject of the Kerr rotating black hole there is as yet no widely accepted physically based and pedagogically viable ansatz suitable for deriving the Kerr solution without significant computational effort. (Typically involving computer-aided symbolic algebra.) Perhaps the closest one gets in this regard is the Newman-Janis trick; a trick which requires several physically unmotivated choices in order to work. Herein we shall try to make some progress on this issue by using a non-ortho-normal tetrad based on oblate spheroidal coordinates to absorb as much of the messy angular dependence as possible, leaving one to deal with a relatively simple angle-independent tetrad-component metric. That is, we shall write $g_{ab} = g_{AB} \; e^A{}_a\; e^B{}_b$ seeking to keep both the tetrad-component metric $g_{AB}$ and the non-ortho-normal co-tetrad $e^A{}_a$ relatively simple but non-trivial. We shall see that it is possible to put all the mass dependence into $g_{AB}$, while the non-ortho-normal co-tetrad $e^A{}_a$ can be chosen to be a mass-independent representation of flat Minkowski space in oblate spheroidal coordinates: $(g_\mathrm{Minkowski})_{ab} = \eta_{AB} \; e^A{}_a\; e^B{}_b$. This procedure separates out, to the greatest extent possible, the mass dependence from the rotational dependence, and makes the Kerr solution perhaps a little less mysterious. |
1609.02287 | German Sharov | Supriya Pan and German S. Sharov | A model with interaction of dark components and recent observational
data | 16 pages, 5 figures, 4 tables; accepted for publication in Mon. Not.
Roy. Astron. Soc | null | 10.1093/mnras/stx2278 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the proposed model with interaction between dark energy and dark matter,
we consider cosmological scenarios with different equations of state ($w_d$)
for dark energy. For both constant and variable equation of state, we analyze
solutions for dark energy and dark matter in seven variants of the model. We
investigate exact analytic solutions for $w_d={}$ constant equation of state,
and several variants of the model for variable $w_d$. These scenarios are
tested with the current astronomical data from Type Ia Supernovae, baryon
acoustic oscillations, Hubble parameter $H (z)$ and the cosmic microwave
background radiation. Finally, we make a statistical comparison of our
interacting model with $\Lambda$CDM as well as with some other well known
non-interacting cosmological models.
| [
{
"created": "Thu, 8 Sep 2016 06:36:06 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Sep 2017 08:32:50 GMT",
"version": "v2"
}
] | 2017-10-18 | [
[
"Pan",
"Supriya",
""
],
[
"Sharov",
"German S.",
""
]
] | In the proposed model with interaction between dark energy and dark matter, we consider cosmological scenarios with different equations of state ($w_d$) for dark energy. For both constant and variable equation of state, we analyze solutions for dark energy and dark matter in seven variants of the model. We investigate exact analytic solutions for $w_d={}$ constant equation of state, and several variants of the model for variable $w_d$. These scenarios are tested with the current astronomical data from Type Ia Supernovae, baryon acoustic oscillations, Hubble parameter $H (z)$ and the cosmic microwave background radiation. Finally, we make a statistical comparison of our interacting model with $\Lambda$CDM as well as with some other well known non-interacting cosmological models. |
2112.07808 | Karen Yagdjian | Karen Yagdjian | Huygens' principle for the spin-1/2 particle in spacetime of
non-constant curvature | null | null | null | null | gr-qc math-ph math.AP math.MP | http://creativecommons.org/licenses/by/4.0/ | In this article we give sufficient and necessary conditions for the validity
of the Huygens' principle for the Dirac operator in the non-constant curvature
spacetime of the Friedmann-Lema\^itre-Robertson-Walker models of cosmology. The
Huygens' principle discussed for the equation of a particle with mass $m=0$ as
well as a massive spin-1/2 particle (field) undergoing a red shift of its
wavelength as the universe expands.
| [
{
"created": "Wed, 15 Dec 2021 00:25:34 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Dec 2021 18:35:13 GMT",
"version": "v2"
},
{
"created": "Thu, 21 Jul 2022 19:34:55 GMT",
"version": "v3"
}
] | 2022-07-25 | [
[
"Yagdjian",
"Karen",
""
]
] | In this article we give sufficient and necessary conditions for the validity of the Huygens' principle for the Dirac operator in the non-constant curvature spacetime of the Friedmann-Lema\^itre-Robertson-Walker models of cosmology. The Huygens' principle discussed for the equation of a particle with mass $m=0$ as well as a massive spin-1/2 particle (field) undergoing a red shift of its wavelength as the universe expands. |
1104.3180 | Yun Soo Myung | Yun Soo Myung | Instability of rotating black hole in a limited form of $f(R)$ gravity | 14 pages, no figure, title changed slightly, version to appear in PRD | Phys.Rev.D84:024048,2011 | 10.1103/PhysRevD.84.024048 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the stability of $f(R)$-rotating (Kerr) black hole obtained
from a limited form of $f(R)$ gravity. In order to avoid the difficulty of
handling fourth order linearized equations, we transform this form of $f(R)$
gravity into the scalar-tensor theory by introducing two auxiliary scalars. In
this case, the linearized curvature scalar equation leads to a massive scalaron
equation. It turns out that the $f(R)$-rotating black hole is unstable because
of the superradiant instability known as the black-hole bomb idea.
| [
{
"created": "Sat, 16 Apr 2011 00:26:11 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Jun 2011 22:19:49 GMT",
"version": "v2"
}
] | 2011-08-12 | [
[
"Myung",
"Yun Soo",
""
]
] | We investigate the stability of $f(R)$-rotating (Kerr) black hole obtained from a limited form of $f(R)$ gravity. In order to avoid the difficulty of handling fourth order linearized equations, we transform this form of $f(R)$ gravity into the scalar-tensor theory by introducing two auxiliary scalars. In this case, the linearized curvature scalar equation leads to a massive scalaron equation. It turns out that the $f(R)$-rotating black hole is unstable because of the superradiant instability known as the black-hole bomb idea. |
gr-qc/0506136 | Warren G. Anderson | Warren G. Anderson and Alan G. Wiseman | A matched expansion approach to practical self-force calculations | IOP style, 8 eps figures, accepted for publication in a special issue
of Classical and Quantum Gravity | Class.Quant.Grav. 22 (2005) S783-S800 | 10.1088/0264-9381/22/15/010 | null | gr-qc | null | We discuss a practical method to compute the self-force on a particle moving
through a curved spacetime. This method involves two expansions to calculate
the self-force, one arising from the particle's immediate past and the other
from the more distant past. The expansion in the immediate past is a covariant
Taylor series and can be carried out for all geometries. The more distant
expansion is a mode sum, and may be carried out in those cases where the wave
equation for the field mediating the self-force admits a mode expansion of the
solution. In particular, this method can be used to calculate the gravitational
self-force for a particle of mass mu orbiting a black hole of mass M to order
mu^2, provided mu/M << 1. We discuss how to use these two expansions to
construct a full self-force, and in particular investigate criteria for
matching the two expansions. As with all methods of computing self-forces for
particles moving in black hole spacetimes, one encounters considerable
technical difficulty in applying this method; nevertheless, it appears that the
convergence of each series is good enough that a practical implementation may
be plausible.
| [
{
"created": "Wed, 29 Jun 2005 16:14:00 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Anderson",
"Warren G.",
""
],
[
"Wiseman",
"Alan G.",
""
]
] | We discuss a practical method to compute the self-force on a particle moving through a curved spacetime. This method involves two expansions to calculate the self-force, one arising from the particle's immediate past and the other from the more distant past. The expansion in the immediate past is a covariant Taylor series and can be carried out for all geometries. The more distant expansion is a mode sum, and may be carried out in those cases where the wave equation for the field mediating the self-force admits a mode expansion of the solution. In particular, this method can be used to calculate the gravitational self-force for a particle of mass mu orbiting a black hole of mass M to order mu^2, provided mu/M << 1. We discuss how to use these two expansions to construct a full self-force, and in particular investigate criteria for matching the two expansions. As with all methods of computing self-forces for particles moving in black hole spacetimes, one encounters considerable technical difficulty in applying this method; nevertheless, it appears that the convergence of each series is good enough that a practical implementation may be plausible. |
0802.3335 | Burkhard Kleihaus | Rustam Ibadov, Burkhard Kleihaus, Jutta Kunz and Michael Leissner | Gravitating Sphaleron-Antisphaleron Systems | 7 pages, 3 figures | Phys.Lett.B663:136-140,2008 | 10.1016/j.physletb.2008.03.055 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present new classical solutions of Einstein-Yang-Mills-Higgs theory,
representing gravitating sphaleron-antisphaleron pair, chain and vortex ring
solutions. In these static axially symmetric solutions, the Higgs field
vanishes on isolated points on the symmetry axis, or on rings centered around
the symmetry axis. We compare these solutions to gravitating
monopole-antimonopole systems, associating monopole-antimonopole pairs with
sphalerons.
| [
{
"created": "Fri, 22 Feb 2008 15:16:06 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Ibadov",
"Rustam",
""
],
[
"Kleihaus",
"Burkhard",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Leissner",
"Michael",
""
]
] | We present new classical solutions of Einstein-Yang-Mills-Higgs theory, representing gravitating sphaleron-antisphaleron pair, chain and vortex ring solutions. In these static axially symmetric solutions, the Higgs field vanishes on isolated points on the symmetry axis, or on rings centered around the symmetry axis. We compare these solutions to gravitating monopole-antimonopole systems, associating monopole-antimonopole pairs with sphalerons. |
gr-qc/9506090 | null | Giampiero Esposito | Alpha Surfaces for Complex Space-Times with Torsion | 7 pages, plain-tex, published in Nuovo Cimento B, volume 108, pages
123-125, year 1993 | NuovoCim.B108:123-126,1993 | 10.1007/BF02874404 | DSF 91/20 | gr-qc | null | This paper studies necessary conditions for the existence of alpha-surfaces
in complex space-time manifolds with nonvanishing torsion. For these manifolds,
Lie brackets of vector fields and spinor Ricci identities contain explicitly
the effects of torsion. This leads to an integrability condition for
alpha-surfaces which does not involve just the self-dual Weyl spinor, as in
complex general relativity, but also the torsion spinor, in a nonlinear way,
and its covariant derivative. Interestingly, a particular solution of the
integrability condition is given by conformally right-flat and
right-torsion-free space-times.
| [
{
"created": "Sat, 1 Jul 1995 20:03:10 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Esposito",
"Giampiero",
""
]
] | This paper studies necessary conditions for the existence of alpha-surfaces in complex space-time manifolds with nonvanishing torsion. For these manifolds, Lie brackets of vector fields and spinor Ricci identities contain explicitly the effects of torsion. This leads to an integrability condition for alpha-surfaces which does not involve just the self-dual Weyl spinor, as in complex general relativity, but also the torsion spinor, in a nonlinear way, and its covariant derivative. Interestingly, a particular solution of the integrability condition is given by conformally right-flat and right-torsion-free space-times. |
2308.01179 | Clare Burrage | Kate Clements and Benjamin Elder and Lucia Hackermueller and Mark
Fromhold and Clare Burrage | Detecting Dark Domain Walls | 8 pages, 3 figures | null | null | null | gr-qc astro-ph.CO hep-ex quant-ph | http://creativecommons.org/licenses/by/4.0/ | Light scalar fields, with double well potentials and direct matter couplings,
undergo density driven phase transitions, leading to the formation of domain
walls. Such theories could explain dark energy, dark matter or source the
nanoHz gravitational-wave background. We describe an experiment that could be
used to detect such domain walls in a laboratory experiment, solving for the
scalar field profile, and showing how the domain wall affects the motion of a
test particle. We find that, in currently unconstrained regions of parameter
space, the domain walls leave detectable signatures.
| [
{
"created": "Wed, 2 Aug 2023 14:39:50 GMT",
"version": "v1"
}
] | 2023-08-03 | [
[
"Clements",
"Kate",
""
],
[
"Elder",
"Benjamin",
""
],
[
"Hackermueller",
"Lucia",
""
],
[
"Fromhold",
"Mark",
""
],
[
"Burrage",
"Clare",
""
]
] | Light scalar fields, with double well potentials and direct matter couplings, undergo density driven phase transitions, leading to the formation of domain walls. Such theories could explain dark energy, dark matter or source the nanoHz gravitational-wave background. We describe an experiment that could be used to detect such domain walls in a laboratory experiment, solving for the scalar field profile, and showing how the domain wall affects the motion of a test particle. We find that, in currently unconstrained regions of parameter space, the domain walls leave detectable signatures. |
2308.05573 | Bayram Tekin | Zeynep Tugce Ozkarsligil, Bayram Tekin | A Systematic Construction of Kastor-Traschen Currents and their
Extensions to Generic Powers of Curvature | 11 pages, v2 matches the published version | Phys.Rev.D 108 (2023) 8, 084050 | 10.1103/PhysRevD.108.084050 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Kastor and Traschen constructed totally anti-symmetric conserved currents
that are linear in the Riemann curvature in spacetimes admitting Killing-Yano
tensors. The construction does not refer to any field equations and is built on
the algebraic and differential symmetries of the Riemann tensor as well as on
the Killing-Yano equation. Here we give a systematic generalization of their
work and find divergence-free currents that are built from the powers of the
curvature tensor. A rank-4 divergence-free tensor that is constructed from the
powers of the curvature tensor plays a major role here and it comes from the
Lanczos-Lovelock theory.
| [
{
"created": "Thu, 10 Aug 2023 13:36:57 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Oct 2023 12:48:35 GMT",
"version": "v2"
}
] | 2023-11-01 | [
[
"Ozkarsligil",
"Zeynep Tugce",
""
],
[
"Tekin",
"Bayram",
""
]
] | Kastor and Traschen constructed totally anti-symmetric conserved currents that are linear in the Riemann curvature in spacetimes admitting Killing-Yano tensors. The construction does not refer to any field equations and is built on the algebraic and differential symmetries of the Riemann tensor as well as on the Killing-Yano equation. Here we give a systematic generalization of their work and find divergence-free currents that are built from the powers of the curvature tensor. A rank-4 divergence-free tensor that is constructed from the powers of the curvature tensor plays a major role here and it comes from the Lanczos-Lovelock theory. |
1007.4126 | Christian Corda cordac | Christian Corda | Presentation of the Second Big Challenge Symposium - The Big Challenge
of Cosmological Understanding: Gravitation, Dark Matter and Dark Energy.
Towards New Scenarios | To appear in the AIP Proceedings of the 8th International Conference
of Numerical Analysis and Applied Mathematics, Hotel Rodos Palace, Rhodes,
Greece, 1925 September 2010 | AIP Conf. Proc. 1281:845,2010 | 10.1063/1.3498619 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This Symposium is devoted to the Memory of Lev Kofman,
June-17-1957-November-12-2009.
The accelerated expansion of the Universe, which is today observed, shows
that cosmological dynamics is dominated by the so-called Dark Energy field
which provides a large negative pressure. This is the standard picture, in
which such new ingredient is considered as a source of the right hand side of
the field equations. It should be some form of non-clustered non-zero vacuum
energy which, together with the clustered Dark Matter, drives the global
dynamics. This is the so-called "concordance model" (ACDM) which gives, in
agreement with the Cosmic Microwave Background Radiation (CMBR), dim Lyman
Limit Systems (LLS) and type la supernovae (SNeIa) data, a good framework to
understand the today observed Universe. However, it presents several
shortcomings as the well known "coincidence" and "cosmological constant"
problems . An alternative approach is to have a better understanding of the
energy concept in General Relativity and also to change the left hand side of
the field equations, and check if observed cosmic dynamics can be achieved by
extending general relativity. In this different context, it is not required to
search candidates for Dark Energy and Dark Matter, which till now have not been
found. Rather, one can only stand on the "observed" ingredients: curvature and
baryon matter, to account for the observations. Considering this point of view,
one can think of that gravity is not scale-invariant. The goal of this
Symposium is to obtain a tapestry of the present status of theory and
observations concerning Gravitation and Dark Universe.
| [
{
"created": "Fri, 23 Jul 2010 13:33:24 GMT",
"version": "v1"
}
] | 2015-05-19 | [
[
"Corda",
"Christian",
""
]
] | This Symposium is devoted to the Memory of Lev Kofman, June-17-1957-November-12-2009. The accelerated expansion of the Universe, which is today observed, shows that cosmological dynamics is dominated by the so-called Dark Energy field which provides a large negative pressure. This is the standard picture, in which such new ingredient is considered as a source of the right hand side of the field equations. It should be some form of non-clustered non-zero vacuum energy which, together with the clustered Dark Matter, drives the global dynamics. This is the so-called "concordance model" (ACDM) which gives, in agreement with the Cosmic Microwave Background Radiation (CMBR), dim Lyman Limit Systems (LLS) and type la supernovae (SNeIa) data, a good framework to understand the today observed Universe. However, it presents several shortcomings as the well known "coincidence" and "cosmological constant" problems . An alternative approach is to have a better understanding of the energy concept in General Relativity and also to change the left hand side of the field equations, and check if observed cosmic dynamics can be achieved by extending general relativity. In this different context, it is not required to search candidates for Dark Energy and Dark Matter, which till now have not been found. Rather, one can only stand on the "observed" ingredients: curvature and baryon matter, to account for the observations. Considering this point of view, one can think of that gravity is not scale-invariant. The goal of this Symposium is to obtain a tapestry of the present status of theory and observations concerning Gravitation and Dark Universe. |
gr-qc/0408071 | Brian Edgar | S. Brian Edgar and Jos\'e M. M. Senovilla | A local potential for the Weyl tensor in all dimensions | 7 pages; Latex | Class.Quant.Grav. 21 (2004) L133 | 10.1088/0264-9381/21/22/L01 | null | gr-qc math-ph math.DG math.MP | null | In all dimensions and arbitrary signature, we demonstrate the existence of a
new local potential -- a double (2,3)-form -- for the Weyl curvature tensor,
and more generally for all tensors with the symmetry properties of the Weyl
curvature tensor. The classical four-dimensional Lanczos potential for a Weyl
tensor -- a double (2,1)-form -- is proven to be a particular case of the new
potential: its double dual.
| [
{
"created": "Fri, 20 Aug 2004 12:03:50 GMT",
"version": "v1"
}
] | 2016-08-16 | [
[
"Edgar",
"S. Brian",
""
],
[
"Senovilla",
"José M. M.",
""
]
] | In all dimensions and arbitrary signature, we demonstrate the existence of a new local potential -- a double (2,3)-form -- for the Weyl curvature tensor, and more generally for all tensors with the symmetry properties of the Weyl curvature tensor. The classical four-dimensional Lanczos potential for a Weyl tensor -- a double (2,1)-form -- is proven to be a particular case of the new potential: its double dual. |
gr-qc/0310005 | Maciej Dunajski | Maciej Dunajski, Maciej Przanowski | Null K\"ahler structures, Symmetries and Integrability | Text of a talk given at the conference on "Mathematical Physics,
General Relativity and Cosmology", held in honour of Professor Jerzy
Plebanski. To appear in the Proceedings | Topics in Mathematical Physics, General Relativity and Cosmology
in Honor of Jerzy Plebanski, ed. Hugo Garcia-Compean, Bogdan Mielnik, Merced
Montesinos & Maciej Przanowski. World Scientific 2006. | null | DAMTP-2003-74 | gr-qc hep-th math-ph math.MP nlin.SI | null | We review the integrable systems which arise as symmetry reductions of
Plebanski's heavenly equations, and their generalisations. We also show that
all four-dimensional null Kahler-Einstein (or type N hyper-heavenly) metrics
with symmetry can be found from solutions to a variable coefficient
generalisation of the dispersionless Kadomtsev-Petviashvili equation.
| [
{
"created": "Wed, 1 Oct 2003 15:30:35 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Jul 2004 02:25:31 GMT",
"version": "v2"
},
{
"created": "Wed, 21 Jun 2006 11:59:10 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Dunajski",
"Maciej",
""
],
[
"Przanowski",
"Maciej",
""
]
] | We review the integrable systems which arise as symmetry reductions of Plebanski's heavenly equations, and their generalisations. We also show that all four-dimensional null Kahler-Einstein (or type N hyper-heavenly) metrics with symmetry can be found from solutions to a variable coefficient generalisation of the dispersionless Kadomtsev-Petviashvili equation. |
gr-qc/9209010 | Sam Finn | Lee Samuel Finn | Detection, Measurement and Gravitational Radiation | 37 pages (plus 6 figures), LaTeX/REVTEX | Phys.Rev.D46:5236-5249,1992 | 10.1103/PhysRevD.46.5236 | NU-GR-1 | gr-qc astro-ph | null | Here I examine how to determine the sensitivity of the LIGO, VIRGO, and LAGOS
gravitational wave detectors to sources of gravitational radiation by
considering the process by which data are analyzed in a noisy detector. By
constructing the probability that the detector output is consistent with the
presence of a signal, I show how to (1) quantify the uncertainty that the
output contains a signal and is not simply noise, and (2) construct the
probability distribution that the signal parameterization has a certain value.
From the distribution and its mode I determine volumes $V(P)$ in parameter
space such that actual signal parameters are in $V(P)$ with probability $P$. If
we are {\em designing} a detector, or determining the suitability of an
existing detector for observing a new source, then we don't have detector
output to analyze but are interested in the ``most likely'' response of the
detector to a signal. I exploit the techniques just described to determine the
``most likely'' volumes $V(P)$ for detector output corresponding to the source.
Finally, as an example, I apply these techniques to anticipate the sensitivity
of the LIGO and LAGOS detectors to the gravitational radiation from a perturbed
Kerr black hole.
| [
{
"created": "Thu, 24 Sep 1992 16:36:00 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Finn",
"Lee Samuel",
""
]
] | Here I examine how to determine the sensitivity of the LIGO, VIRGO, and LAGOS gravitational wave detectors to sources of gravitational radiation by considering the process by which data are analyzed in a noisy detector. By constructing the probability that the detector output is consistent with the presence of a signal, I show how to (1) quantify the uncertainty that the output contains a signal and is not simply noise, and (2) construct the probability distribution that the signal parameterization has a certain value. From the distribution and its mode I determine volumes $V(P)$ in parameter space such that actual signal parameters are in $V(P)$ with probability $P$. If we are {\em designing} a detector, or determining the suitability of an existing detector for observing a new source, then we don't have detector output to analyze but are interested in the ``most likely'' response of the detector to a signal. I exploit the techniques just described to determine the ``most likely'' volumes $V(P)$ for detector output corresponding to the source. Finally, as an example, I apply these techniques to anticipate the sensitivity of the LIGO and LAGOS detectors to the gravitational radiation from a perturbed Kerr black hole. |
gr-qc/9812060 | Iosif B. Khriplovich | I.B. Khriplovich | Radiation of Charged Particles by Charged Black Hole | 10 pages, latex, 4 ps-figures | null | 10.1134/1.558889 | null | gr-qc hep-th | null | The probability of a charged particle production by the electric field of a
charged black hole depends essentially on the particle energy. This probability
is found in the nonrelativistic and ultrarelativistic limits. The range of
values for the mass and charge of a black hole is indicated where the discussed
mechanism of radiation is dominating over the Hawking one.
| [
{
"created": "Thu, 17 Dec 1998 10:30:31 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Khriplovich",
"I. B.",
""
]
] | The probability of a charged particle production by the electric field of a charged black hole depends essentially on the particle energy. This probability is found in the nonrelativistic and ultrarelativistic limits. The range of values for the mass and charge of a black hole is indicated where the discussed mechanism of radiation is dominating over the Hawking one. |
2403.01910 | Luca Cafaro | Luca Cafaro, Jerzy Lewandowski | Status of Birkhoff's theorem in polymerized semiclassical regime of Loop
Quantum Gravity | 13 pages, 3 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The collapse of a spherically symmetric ball of dust has been intensively
studied in Loop Quantum Gravity (LQG). From a quantum theory, it is possible to
recover a semiclassical regime through a polymerization procedure. In this
setting, general solutions to the polymerized Einstein field equations (PEFE)
will be discussed both for the interior and the exterior of the dust cloud.
Exterior solutions are particularly interesting since they may lead to a
semiclassical version of the Birkhoff's theorem. It is seen that if time
independence of the vacuum is imposed, there exists a unique class of solutions
depending on two parameters. Nevertheless, the possibility of more intricate
time dependent solutions is not ruled out completely. Ultimately, these results
will be compared to a model of spherical collapse obtained independently from
the Einstein equations.
| [
{
"created": "Mon, 4 Mar 2024 10:18:57 GMT",
"version": "v1"
},
{
"created": "Thu, 16 May 2024 10:19:31 GMT",
"version": "v2"
}
] | 2024-05-17 | [
[
"Cafaro",
"Luca",
""
],
[
"Lewandowski",
"Jerzy",
""
]
] | The collapse of a spherically symmetric ball of dust has been intensively studied in Loop Quantum Gravity (LQG). From a quantum theory, it is possible to recover a semiclassical regime through a polymerization procedure. In this setting, general solutions to the polymerized Einstein field equations (PEFE) will be discussed both for the interior and the exterior of the dust cloud. Exterior solutions are particularly interesting since they may lead to a semiclassical version of the Birkhoff's theorem. It is seen that if time independence of the vacuum is imposed, there exists a unique class of solutions depending on two parameters. Nevertheless, the possibility of more intricate time dependent solutions is not ruled out completely. Ultimately, these results will be compared to a model of spherical collapse obtained independently from the Einstein equations. |
2402.04091 | Jo\~ao Lu\'is Rosa | Jo\~ao Lu\'is Rosa, Tom Zlosnik | Sudden cosmological singularities in Aether scalar-tensor theories | 14 pages, 9 figures | Phys. Rev. D 109, 104077 (2024) | 10.1103/PhysRevD.109.104077 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we analyze the possibility of sudden cosmological singularities,
also known as type-II singularities, in the background of a
Friedmann-Lema\^itre-Robertson-Walker (FLRW) geometry in an extension of
General Relativity (GR) known as Aether scalar-tensor theories (AeST).
Similarly to several scalar-tensor theories, we observe that sudden
singularities may occur in certain AeST models at the level of the second-order
time derivative of the scale factor. These singularities can either be induced
by AeST's scalar field itself in the absence of a fluid matter component, or by
a divergence of the pressure component of the fluid. In the latter case, one
observes that the second-order time derivative of the scalar field $Q$ is also
divergent at the instant the sudden singularity happens. We show that the
sudden singularities can be prevented by an appropriate choice of the action,
for which a divergence in the scalar field compensates the divergence in the
pressure component of the matter fluid, thus preserving the regularity of the
scale factor and all its time derivatives. For the models featuring a sudden
singularity in the second-order time derivative of the scale factor, an
analysis of the cosmographic parameters, namely the Hubble and the deceleration
parameters, indicates that cosmological models featuring sudden singularities
are allowed by the current cosmological measurements. Furthermore, an analysis
of the jerk parameter favours cosmological models that attain a sudden
singularity at a faster rate, up to a time of at most $t_s\sim 1.2 t_0$, where
$t_0$ is the current age of the universe, and with negative values for the
cosmological snap parameter.
| [
{
"created": "Tue, 6 Feb 2024 15:48:08 GMT",
"version": "v1"
}
] | 2024-05-30 | [
[
"Rosa",
"João Luís",
""
],
[
"Zlosnik",
"Tom",
""
]
] | In this work we analyze the possibility of sudden cosmological singularities, also known as type-II singularities, in the background of a Friedmann-Lema\^itre-Robertson-Walker (FLRW) geometry in an extension of General Relativity (GR) known as Aether scalar-tensor theories (AeST). Similarly to several scalar-tensor theories, we observe that sudden singularities may occur in certain AeST models at the level of the second-order time derivative of the scale factor. These singularities can either be induced by AeST's scalar field itself in the absence of a fluid matter component, or by a divergence of the pressure component of the fluid. In the latter case, one observes that the second-order time derivative of the scalar field $Q$ is also divergent at the instant the sudden singularity happens. We show that the sudden singularities can be prevented by an appropriate choice of the action, for which a divergence in the scalar field compensates the divergence in the pressure component of the matter fluid, thus preserving the regularity of the scale factor and all its time derivatives. For the models featuring a sudden singularity in the second-order time derivative of the scale factor, an analysis of the cosmographic parameters, namely the Hubble and the deceleration parameters, indicates that cosmological models featuring sudden singularities are allowed by the current cosmological measurements. Furthermore, an analysis of the jerk parameter favours cosmological models that attain a sudden singularity at a faster rate, up to a time of at most $t_s\sim 1.2 t_0$, where $t_0$ is the current age of the universe, and with negative values for the cosmological snap parameter. |
gr-qc/9306026 | Alberto Vazquez Saa | Alberto Saa | Gauge fields on Riemann-Cartan space-times | 16 pages, IFUSP/P-1031 | Mod.Phys.Lett. A9 (1994) 971-982 | 10.1142/S0217732394000812 | null | gr-qc | null | Gauge fields are described on an Riemann-Cartan space-time by means of
tensor-valued differential forms and exterior calculus. It is shown that
minimal coupling procedure leads to a gauge invariant theory where gauge fields
interact with torsion, and that consistency conditions for the gauge fields
impose restrictions in the non-Riemannian structure of space-time. The new
results differ from the well established ones obtained by using minimal
coupling procedure at the action formulation. The sources of these differences
are pointed out and discussed.
| [
{
"created": "Tue, 22 Jun 1993 14:18:13 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Saa",
"Alberto",
""
]
] | Gauge fields are described on an Riemann-Cartan space-time by means of tensor-valued differential forms and exterior calculus. It is shown that minimal coupling procedure leads to a gauge invariant theory where gauge fields interact with torsion, and that consistency conditions for the gauge fields impose restrictions in the non-Riemannian structure of space-time. The new results differ from the well established ones obtained by using minimal coupling procedure at the action formulation. The sources of these differences are pointed out and discussed. |
1103.5912 | Th. M. Nieuwenhuizen | Th. M. Nieuwenhuizen | Exact Schwarzschild-de Sitter black holes in a family of massive gravity
models | 4 pages | Phys.Rev.D84:024038,2011 | 10.1103/PhysRevD.84.024038 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Schwarzschild-de Sitter and Reissner-Nordstr\"om-de Sitter black hole
metrics appear as exact solutions in the recently formulated massive gravity of
de Rham, Gabadadze and Tolley (dRGT), where the mass term sets the curvature
scale. They occur within a two-parameter family of dGRT mass terms. They show
no trace of a cloud of scalar graviton modes, and in the limit of vanishing
graviton mass they go smoothly to the Schwarzschild and Reissner-Nordstr\"om
metrics.
| [
{
"created": "Tue, 29 Mar 2011 17:53:05 GMT",
"version": "v1"
}
] | 2011-08-09 | [
[
"Nieuwenhuizen",
"Th. M.",
""
]
] | The Schwarzschild-de Sitter and Reissner-Nordstr\"om-de Sitter black hole metrics appear as exact solutions in the recently formulated massive gravity of de Rham, Gabadadze and Tolley (dRGT), where the mass term sets the curvature scale. They occur within a two-parameter family of dGRT mass terms. They show no trace of a cloud of scalar graviton modes, and in the limit of vanishing graviton mass they go smoothly to the Schwarzschild and Reissner-Nordstr\"om metrics. |
1403.4710 | Jishnu Suresh | Jishnu Suresh, Tharanath R, Nijo Varghese and V C Kuriakose | Thermodynamics and Thermodynamic geometry of Park black hole | 11 pages, 9 figures | Eur. Phys. J. C (2014) 74:2819 | 10.1140/epjc/s10052-014-2819-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the thermodynamics and thermodynamic geometry of Park black hole in
Ho\v{r}ava gravity. By incorporating the ideas of differential geometry, we
have investigated the thermodynamics using Weinhold geometry and Ruppeiner
geometry. We have also analyzed it in the context of newly developed
geometrothermodynamics(GTD). Divergence of specific heat is associated with the
second order phase transition of black hole. Here in the context of Park black
hole, both Weinhold's metric and Ruppeiner's metric well explain this phase
transition. But these explanations depend on the choice of potential. Hence the
Legendre invariant GTD is used, and with the true singularities in the
curvature scalar, GTD well explain the second order phase transition. All these
methods together give an exact idea of all the behaviors of the Park black hole
thermodynamics.
| [
{
"created": "Wed, 19 Mar 2014 07:07:29 GMT",
"version": "v1"
}
] | 2014-05-05 | [
[
"Suresh",
"Jishnu",
""
],
[
"R",
"Tharanath",
""
],
[
"Varghese",
"Nijo",
""
],
[
"Kuriakose",
"V C",
""
]
] | We study the thermodynamics and thermodynamic geometry of Park black hole in Ho\v{r}ava gravity. By incorporating the ideas of differential geometry, we have investigated the thermodynamics using Weinhold geometry and Ruppeiner geometry. We have also analyzed it in the context of newly developed geometrothermodynamics(GTD). Divergence of specific heat is associated with the second order phase transition of black hole. Here in the context of Park black hole, both Weinhold's metric and Ruppeiner's metric well explain this phase transition. But these explanations depend on the choice of potential. Hence the Legendre invariant GTD is used, and with the true singularities in the curvature scalar, GTD well explain the second order phase transition. All these methods together give an exact idea of all the behaviors of the Park black hole thermodynamics. |
gr-qc/0310007 | Antoni Arbona Nadal | A. Arbona | Is a classical Euclidean TOE reasonable? | RevTex4, 36 pages, no figures | null | null | null | gr-qc quant-ph | null | We analyze both the feasibility and reasonableness of a classical Euclidean
Theory of Everything (TOE), which we understand as a TOE based on an Euclidean
space and an absolute time over which deterministic models of particles and
forces are built. The possible axiomatic complexity of a TOE in such a
framework is considered and compared to the complexity of the assumptions
underlying the Standard Model. Current approaches to relevant (for our
purposes) reformulations of Special Relativity, General Relativity, inertia
models and Quantum Theory are summarized, and links between some of these
reformulations are exposed. A qualitative framework is suggested for a research
program on a classical Euclidean TOE. Within this framework an underlying basis
is suggested, in particular, for the Principle of Relativity and Principle of
Equivalence. A model for gravity as an inertial phenomenon is proposed. Also, a
basis for quantum indeterminacy and wave function collapse is suggested in the
framework.
| [
{
"created": "Wed, 1 Oct 2003 22:45:29 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Arbona",
"A.",
""
]
] | We analyze both the feasibility and reasonableness of a classical Euclidean Theory of Everything (TOE), which we understand as a TOE based on an Euclidean space and an absolute time over which deterministic models of particles and forces are built. The possible axiomatic complexity of a TOE in such a framework is considered and compared to the complexity of the assumptions underlying the Standard Model. Current approaches to relevant (for our purposes) reformulations of Special Relativity, General Relativity, inertia models and Quantum Theory are summarized, and links between some of these reformulations are exposed. A qualitative framework is suggested for a research program on a classical Euclidean TOE. Within this framework an underlying basis is suggested, in particular, for the Principle of Relativity and Principle of Equivalence. A model for gravity as an inertial phenomenon is proposed. Also, a basis for quantum indeterminacy and wave function collapse is suggested in the framework. |
1308.5675 | Ghulam Abbas | M. Sharif, G. Abbas | Dynamics of Charged Radiating Collapse in Modified Gauss-Bonnet Gravity | 15 pages, no figure, Accepted for publication in Eur. Phys. J. Plus.
arXiv admin note: text overlap with arXiv:1302.1173 | Eur. Phys. J. Plus (2013) 128: 102 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper deals with the dynamics of a shearfree charged radiating collapse
in modified Gauss-Bonnet gravity. The field equations for shearfree spherical
interior geometry of a charged dissipative star are formulated. To study the
dynamical behavior of collapsing matter, we derive the dynamical as well as
transport equations. We conclude that the gravitational force in modified
Gauss-Bonnet gravity is much stronger as compared to general relativity which
implies the increase in the rate of collapse. Finally, we study the effect of
charge on the dynamics of collapse.
| [
{
"created": "Mon, 26 Aug 2013 07:53:52 GMT",
"version": "v1"
}
] | 2013-09-09 | [
[
"Sharif",
"M.",
""
],
[
"Abbas",
"G.",
""
]
] | This paper deals with the dynamics of a shearfree charged radiating collapse in modified Gauss-Bonnet gravity. The field equations for shearfree spherical interior geometry of a charged dissipative star are formulated. To study the dynamical behavior of collapsing matter, we derive the dynamical as well as transport equations. We conclude that the gravitational force in modified Gauss-Bonnet gravity is much stronger as compared to general relativity which implies the increase in the rate of collapse. Finally, we study the effect of charge on the dynamics of collapse. |
0902.3763 | Giovanni Salesi | G. Salesi and E. Di Grezia | Black hole evaporation within a momentum-dependent metric | null | Phys.Rev.D79:104009,2009 | 10.1103/PhysRevD.79.104009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the black hole thermodynamics in a "deformed" relativity
framework where the energy-momentum dispersion law is Lorentz-violating and the
Schwarzchild-like metric is momentum-dependent with a Planckian cut-off. We
obtain net deviations of the basic thermodynamical quantities from the
Hawking-Bekenstein predictions: actually, the black hole evaporation is
expected to quit at a nonzero critical mass value (of the order of the Planck
mass), leaving a zero temperature remnant, and avoiding a spacetime
singularity. Quite surprisingly, the present semiclassical corrections to black
hole temperature, entropy, and heat capacity turn out to be identical to the
ones obtained within some quantum approaches.
| [
{
"created": "Sun, 22 Feb 2009 02:22:27 GMT",
"version": "v1"
},
{
"created": "Sun, 8 Mar 2009 00:53:47 GMT",
"version": "v2"
},
{
"created": "Tue, 19 May 2009 22:43:26 GMT",
"version": "v3"
}
] | 2009-05-22 | [
[
"Salesi",
"G.",
""
],
[
"Di Grezia",
"E.",
""
]
] | We investigate the black hole thermodynamics in a "deformed" relativity framework where the energy-momentum dispersion law is Lorentz-violating and the Schwarzchild-like metric is momentum-dependent with a Planckian cut-off. We obtain net deviations of the basic thermodynamical quantities from the Hawking-Bekenstein predictions: actually, the black hole evaporation is expected to quit at a nonzero critical mass value (of the order of the Planck mass), leaving a zero temperature remnant, and avoiding a spacetime singularity. Quite surprisingly, the present semiclassical corrections to black hole temperature, entropy, and heat capacity turn out to be identical to the ones obtained within some quantum approaches. |
1807.06554 | Gregory V. Vereshchagin | Suzana Bedi\'c and Gregory Vereshchagin | Probability of inflation in Loop Quantum Cosmology | Accepted for publication in Phys. Rev. D | Phys. Rev. D 99, 043512 (2019) | 10.1103/PhysRevD.99.043512 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss how initial conditions for cosmological evolution can be defined
in Loop Quantum Cosmology with massive scalar field and how the presence of the
bounce influences the probability of inflation in this theory, compared with
General Relativity. The main finding of the paper is existence of an attractor
in the contracting phase of the universe, which results in special conditions
at the bounce, quite independent on the measure of initial conditions in the
remote past, and hence very specific duration of inflationary stage with the
number of e-foldings about $140$.
| [
{
"created": "Tue, 17 Jul 2018 17:03:07 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Jan 2019 09:32:04 GMT",
"version": "v2"
}
] | 2019-02-15 | [
[
"Bedić",
"Suzana",
""
],
[
"Vereshchagin",
"Gregory",
""
]
] | We discuss how initial conditions for cosmological evolution can be defined in Loop Quantum Cosmology with massive scalar field and how the presence of the bounce influences the probability of inflation in this theory, compared with General Relativity. The main finding of the paper is existence of an attractor in the contracting phase of the universe, which results in special conditions at the bounce, quite independent on the measure of initial conditions in the remote past, and hence very specific duration of inflationary stage with the number of e-foldings about $140$. |
1112.3078 | Chiao-Hsuan Wang | Pisin Chen and Chiao-Hsuan Wang | Where is hbar Hiding in Entropic Gravity? | 8 pages, 2 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The entropic gravity scenario recently proposed by Erik Verlinde reproduced
the Newton's law of purely classical gravity yet the key assumptions of this
approach all have quantum mechanical origins. This is atypical for emergent
phenomena in physics, where the underlying, more fundamental physics often
reveals itself as corrections to the leading classical behavior. So one
naturally wonders: where is hbar hiding in entropic gravity? To address this
question, we first revisit the idea of holographic screen as well as entropy
and its variation law in order to obtain a self-consistent approach to the
problem. Next we argue that when dealing with quantum gravity issues the
generalized uncertainty principle (GUP) should be the more appropriate
foundation. Indeed based on GUP it has been demonstrated that the black hole
Bekenstein entropy area law must be modified not only in the strong but also in
the weak gravity regime. In the weak gravity limit, such a GUP modified entropy
exhibits a logarithmic correction term. When applying it to the entropic
interpretation, we demonstrate that the resulting gravity force law does
include sub-leading order correction terms that depend on hbar. Such deviation
from the classical Newton's law may serve as a probe to the validity of the
entropic gravity postulate.
| [
{
"created": "Wed, 14 Dec 2011 00:32:51 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Nov 2017 20:25:28 GMT",
"version": "v2"
}
] | 2017-11-22 | [
[
"Chen",
"Pisin",
""
],
[
"Wang",
"Chiao-Hsuan",
""
]
] | The entropic gravity scenario recently proposed by Erik Verlinde reproduced the Newton's law of purely classical gravity yet the key assumptions of this approach all have quantum mechanical origins. This is atypical for emergent phenomena in physics, where the underlying, more fundamental physics often reveals itself as corrections to the leading classical behavior. So one naturally wonders: where is hbar hiding in entropic gravity? To address this question, we first revisit the idea of holographic screen as well as entropy and its variation law in order to obtain a self-consistent approach to the problem. Next we argue that when dealing with quantum gravity issues the generalized uncertainty principle (GUP) should be the more appropriate foundation. Indeed based on GUP it has been demonstrated that the black hole Bekenstein entropy area law must be modified not only in the strong but also in the weak gravity regime. In the weak gravity limit, such a GUP modified entropy exhibits a logarithmic correction term. When applying it to the entropic interpretation, we demonstrate that the resulting gravity force law does include sub-leading order correction terms that depend on hbar. Such deviation from the classical Newton's law may serve as a probe to the validity of the entropic gravity postulate. |
gr-qc/0507050 | Valter Moretti | V. Moretti, N. Pinamonti | Black Hole Horizons and Thermodynamics: A Quantum Approach | 21 pages, revised and published version, title changed | Entropy 12:1833-1854,2010 | 10.3390/e12071833 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We focus on quantization of the metric of a black hole restricted to the
Killing horizon with universal radius $r_0$. After imposing spherical symmetry
and after restriction to the Killing horizon, the metric is quantized employing
the chiral currents formalism. Two ``components of the metric'' are indeed
quantized: The former behaves as an affine scalar field under changes of
coordinates, the latter is instead a proper scalar field. The action of the
symplectic group on both fields is realized in terms of certain horizon
diffeomorphisms. Depending on the choice of the vacuum state, such a
representation is unitary. If the reference state of the scalar field is a
coherent state rather than a vacuum, spontaneous breaking of conformal symmetry
arises and the state contains a Bose-Einstein condensate. In this case the
order parameter fixes the actual size of the black hole with respect to $r_0$.
Both the constructed state together with the one associated with the affine
scalar are thermal states (KMS) with respect to Schwarzschild Killing time when
restricted to half horizon. The value of the order parameter fixes the
temperature at the Hawking value as well. As a result, it is found that the
quantum energy and entropy densities coincide with the black hole mass and
entropy, provided the universal parameter $r_0$ is suitably chosen, not
depending on the size of the actual black hole in particular.
| [
{
"created": "Tue, 12 Jul 2005 10:02:10 GMT",
"version": "v1"
},
{
"created": "Sat, 24 Jul 2010 08:50:54 GMT",
"version": "v2"
}
] | 2011-04-07 | [
[
"Moretti",
"V.",
""
],
[
"Pinamonti",
"N.",
""
]
] | We focus on quantization of the metric of a black hole restricted to the Killing horizon with universal radius $r_0$. After imposing spherical symmetry and after restriction to the Killing horizon, the metric is quantized employing the chiral currents formalism. Two ``components of the metric'' are indeed quantized: The former behaves as an affine scalar field under changes of coordinates, the latter is instead a proper scalar field. The action of the symplectic group on both fields is realized in terms of certain horizon diffeomorphisms. Depending on the choice of the vacuum state, such a representation is unitary. If the reference state of the scalar field is a coherent state rather than a vacuum, spontaneous breaking of conformal symmetry arises and the state contains a Bose-Einstein condensate. In this case the order parameter fixes the actual size of the black hole with respect to $r_0$. Both the constructed state together with the one associated with the affine scalar are thermal states (KMS) with respect to Schwarzschild Killing time when restricted to half horizon. The value of the order parameter fixes the temperature at the Hawking value as well. As a result, it is found that the quantum energy and entropy densities coincide with the black hole mass and entropy, provided the universal parameter $r_0$ is suitably chosen, not depending on the size of the actual black hole in particular. |
gr-qc/0012023 | Sergio Dain | Sergio Dain | Initial data for two Kerr-like black holes | revtex, 5 pages, no figures | Phys.Rev.Lett. 87 (2001) 121102 | 10.1103/PhysRevLett.87.121102 | null | gr-qc | null | We prove the existence of a family of initial data for the Einstein vacuum
equation which can be interpreted as the data for two Kerr-like black holes in
arbitrary location and with spin in arbitrary direction. When the mass
parameter of one of them is zero, this family reduces exactly to the Kerr
initial data. The existence proof is based on a general property of the Kerr
metric which can be used in other constructions as well. Further
generalizations are also discussed.
| [
{
"created": "Wed, 6 Dec 2000 09:25:07 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Dain",
"Sergio",
""
]
] | We prove the existence of a family of initial data for the Einstein vacuum equation which can be interpreted as the data for two Kerr-like black holes in arbitrary location and with spin in arbitrary direction. When the mass parameter of one of them is zero, this family reduces exactly to the Kerr initial data. The existence proof is based on a general property of the Kerr metric which can be used in other constructions as well. Further generalizations are also discussed. |
0708.3352 | J. Mark Heinzle | J. Mark Heinzle | Bounds on 2m/r for static perfect fluids | 11 pages | null | null | null | gr-qc | null | For spherically symmetric relativistic perfect fluid models, the well-known
Buchdahl inequality provides the bound $2 M/R \leq 8/9$, where $R$ denotes the
surface radius and $M$ the total mass of a solution. By assuming that the ratio
$p/\rho$ be bounded, where $p$ is the pressure, $\rho$ the density of
solutions, we prove a sharper inequality of the same type, which depends on the
actual bound imposed on $p/\rho$. As a special case, when we assume the
dominant energy condition $p/\rho \leq 1$, we obtain $2 M/R \leq 6/7$.
| [
{
"created": "Fri, 24 Aug 2007 15:00:00 GMT",
"version": "v1"
}
] | 2007-08-27 | [
[
"Heinzle",
"J. Mark",
""
]
] | For spherically symmetric relativistic perfect fluid models, the well-known Buchdahl inequality provides the bound $2 M/R \leq 8/9$, where $R$ denotes the surface radius and $M$ the total mass of a solution. By assuming that the ratio $p/\rho$ be bounded, where $p$ is the pressure, $\rho$ the density of solutions, we prove a sharper inequality of the same type, which depends on the actual bound imposed on $p/\rho$. As a special case, when we assume the dominant energy condition $p/\rho \leq 1$, we obtain $2 M/R \leq 6/7$. |
2001.10683 | Fabi\'an Villalba | Daniel Molano, Fabi\'an Dar\'io Villalba, Leonardo Casta\~neda, Pedro
Bargue\~no | On perturbative constraints for vacuum f(R) gravity | 23 pages, 2 figures. Accepted for publication in Classical and
Quantum Gravity | null | 10.1088/1361-6382/ab8051 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Perturbative techniques are important for modified theories of gravity since
they allow to calculate deviations from General Relativity without recurring to
exact solutions, which can be difficult to find. When applied to models such as
$f(R)$ gravity, these techniques introduce corrections in the field equations
that involve higher order derivatives. Such corrections must be handled
carefully to have a well defined perturbative scheme, and this can be achieved
through the method of perturbative constraints, where the coefficient of the
additional term in the action is used as expansion parameter for the quantities
of interest. In this work, we implement a perturbative framework that compares
solutions in modified theories of gravity with solutions of the Einstein field
equations, by following the guidelines of perturbation theory constructed in
General Relativity together with the perturbative constraints rationale. By
using this formalism, we demonstrate that a consistent $f(R)$ perturbation
theory in vacuum, for an important class of $f(R)$ functions, produces no
additional effects with respect to what is expected from the perturbation
theory of General Relativity. From this result, we argue that there are
fundamental limitations that explain why the solutions of some $f(R)$ models
can be disconnected from their general relativistic counterparts, in the sense
that the limit that leads from the $f(R)$ action to General Relativity does not
transform the solutions accordingly.
| [
{
"created": "Wed, 29 Jan 2020 03:45:20 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Mar 2020 23:06:38 GMT",
"version": "v2"
}
] | 2020-03-18 | [
[
"Molano",
"Daniel",
""
],
[
"Villalba",
"Fabián Darío",
""
],
[
"Castañeda",
"Leonardo",
""
],
[
"Bargueño",
"Pedro",
""
]
] | Perturbative techniques are important for modified theories of gravity since they allow to calculate deviations from General Relativity without recurring to exact solutions, which can be difficult to find. When applied to models such as $f(R)$ gravity, these techniques introduce corrections in the field equations that involve higher order derivatives. Such corrections must be handled carefully to have a well defined perturbative scheme, and this can be achieved through the method of perturbative constraints, where the coefficient of the additional term in the action is used as expansion parameter for the quantities of interest. In this work, we implement a perturbative framework that compares solutions in modified theories of gravity with solutions of the Einstein field equations, by following the guidelines of perturbation theory constructed in General Relativity together with the perturbative constraints rationale. By using this formalism, we demonstrate that a consistent $f(R)$ perturbation theory in vacuum, for an important class of $f(R)$ functions, produces no additional effects with respect to what is expected from the perturbation theory of General Relativity. From this result, we argue that there are fundamental limitations that explain why the solutions of some $f(R)$ models can be disconnected from their general relativistic counterparts, in the sense that the limit that leads from the $f(R)$ action to General Relativity does not transform the solutions accordingly. |
gr-qc/9709014 | Patrick R. Brady | Patrick R. Brady, Chris M. Chambers, and Sergio M. C. V. Goncalves | Phases of massive scalar field collapse | 5 pages, RevTex, 4 postscript figures included using psfig | Phys.Rev.D56:6057-6061,1997 | 10.1103/PhysRevD.56.R6057 | GRP-475 | gr-qc | null | We study critical behavior in the collapse of massive spherically symmetric
scalar fields. We observe two distinct types of phase transition at the
threshold of black hole formation. Type II phase transitions occur when the
radial extent $(\lambda)$ of the initial pulse is less than the Compton
wavelength ($\mu^{-1}$) of the scalar field. The critical solution is that
found by Choptuik in the collapse of massless scalar fields. Type I phase
transitions, where the black hole formation turns on at finite mass, occur when
$\lambda \mu \gg 1$. The critical solutions are unstable soliton stars with
masses $\alt 0.6 \mu^{-1}$. Our results in combination with those obtained for
the collapse of a Yang-Mills field~{[M.~W. Choptuik, T. Chmaj, and P. Bizon,
Phys. Rev. Lett. 77, 424 (1996)]} suggest that unstable, confined solutions to
the Einstein-matter equations may be relevant to the critical point of other
matter models.
| [
{
"created": "Sat, 6 Sep 1997 03:38:14 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Brady",
"Patrick R.",
""
],
[
"Chambers",
"Chris M.",
""
],
[
"Goncalves",
"Sergio M. C. V.",
""
]
] | We study critical behavior in the collapse of massive spherically symmetric scalar fields. We observe two distinct types of phase transition at the threshold of black hole formation. Type II phase transitions occur when the radial extent $(\lambda)$ of the initial pulse is less than the Compton wavelength ($\mu^{-1}$) of the scalar field. The critical solution is that found by Choptuik in the collapse of massless scalar fields. Type I phase transitions, where the black hole formation turns on at finite mass, occur when $\lambda \mu \gg 1$. The critical solutions are unstable soliton stars with masses $\alt 0.6 \mu^{-1}$. Our results in combination with those obtained for the collapse of a Yang-Mills field~{[M.~W. Choptuik, T. Chmaj, and P. Bizon, Phys. Rev. Lett. 77, 424 (1996)]} suggest that unstable, confined solutions to the Einstein-matter equations may be relevant to the critical point of other matter models. |
2309.16461 | Surajit Mandal | Surajit Mandal | Weak Deflection Angle, Hawking Radiation, Greybody Bound and Shadow Cast
for Static Black Hole in the Framework of $f(R)$ Gravity | 49 pages, 16 figures, accepted for publication in Physics of the Dark
Universe (Elsevier) | null | null | null | gr-qc | http://creativecommons.org/licenses/by-sa/4.0/ | In this work, we probe the weak gravitational lensing by a static spherically
symmetric black hole in view of $f(R)$ gravity in the background of the
non-plasma medium (vacuum). We provide a discussion on a light ray in a static
black hole solution in $f(R)$ gravity. To adore this purpose, we find the
Gaussian optical curvature in weak gravitational lensing by utilizing the
optical geometry of this black hole solution. Furthermore, we find the
deflection angle up to the leading order by employing the Gauss-Bonnet theorem.
We present the graphical analysis of the deflection angle with respect to the
various parameters that govern the black hole. Further, we calculate the
Hawking temperature for this black hole via a topological method and compare it
with a standard method of deriving the Hawking temperature. We also analyze the
Schr\"odinger-like Regge-Wheeler equation and derive a bound on the greybody
factor for a static black hole in the framework of $f(R)$ gravity and
graphically inquire that bound converges to 1. We also investigate the
silhouette or shadow generated by this static $f(R)$ black hole. Moreover, we
constrain the non-negative real constant and cosmological constant from the
observed angular diameters of M87* and Sgr A* released by the EHT. We then
probe how cosmological constant, non-negative real constant and mass affected
the radius of shadow. Finally, we demonstrate that, in the eikonal limit, the
real part of scalar field quasinormal mode frequency can be determined from the
shadow radius.
| [
{
"created": "Thu, 28 Sep 2023 14:10:56 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Oct 2023 14:05:55 GMT",
"version": "v2"
}
] | 2023-11-01 | [
[
"Mandal",
"Surajit",
""
]
] | In this work, we probe the weak gravitational lensing by a static spherically symmetric black hole in view of $f(R)$ gravity in the background of the non-plasma medium (vacuum). We provide a discussion on a light ray in a static black hole solution in $f(R)$ gravity. To adore this purpose, we find the Gaussian optical curvature in weak gravitational lensing by utilizing the optical geometry of this black hole solution. Furthermore, we find the deflection angle up to the leading order by employing the Gauss-Bonnet theorem. We present the graphical analysis of the deflection angle with respect to the various parameters that govern the black hole. Further, we calculate the Hawking temperature for this black hole via a topological method and compare it with a standard method of deriving the Hawking temperature. We also analyze the Schr\"odinger-like Regge-Wheeler equation and derive a bound on the greybody factor for a static black hole in the framework of $f(R)$ gravity and graphically inquire that bound converges to 1. We also investigate the silhouette or shadow generated by this static $f(R)$ black hole. Moreover, we constrain the non-negative real constant and cosmological constant from the observed angular diameters of M87* and Sgr A* released by the EHT. We then probe how cosmological constant, non-negative real constant and mass affected the radius of shadow. Finally, we demonstrate that, in the eikonal limit, the real part of scalar field quasinormal mode frequency can be determined from the shadow radius. |
gr-qc/9407020 | Tevian Dray | Stuart Boersma and Tevian Dray | Slicing, Threading & Parametric Manifolds | Plain TeX, 18 pages, 5 PostScript figures (psfig) | Gen.Rel.Grav. 27 (1995) 319-339 | 10.1007/BF02109128 | null | gr-qc | null | We present a unified treatment of the slicing (3+1) and threading (1+3)
decompositions of spacetime in terms of foliations. It is well-known how to
decompose the metric and connection in the slicing picture; this is at the
heart of any initial-value problem in general relativity. We describe here the
analogous problem in the threading picture, recovering the recent results of
Perjes on parametric manifolds.
| [
{
"created": "Fri, 15 Jul 1994 23:37:43 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Boersma",
"Stuart",
""
],
[
"Dray",
"Tevian",
""
]
] | We present a unified treatment of the slicing (3+1) and threading (1+3) decompositions of spacetime in terms of foliations. It is well-known how to decompose the metric and connection in the slicing picture; this is at the heart of any initial-value problem in general relativity. We describe here the analogous problem in the threading picture, recovering the recent results of Perjes on parametric manifolds. |
1307.6655 | Alberto Garcia-Diaz | Alberto A. Garcia-Diaz | Three dimensional stationary cyclic symmetric Einstein-Maxwell
solutions; black holes | null | Annals of Physics {\bf 324} (2009) 2004-2050 | 10.1016/j.aop.2009.04.004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | From a general metric for stationary cyclic symmetric gravitational fields
coupled to Maxwell electromagnetic fields within the $(2+1)$-dimensional
gravity the uniqueness of wide families of exact solutions is established,
among them, all uniform electromagnetic solutions possessing electromagnetic
fields with vanishing covariant derivatives, all fields having constant
electromagnetic invariants $F_{\mu\nu}\,F^{\mu\nu}$ and
$T_{\mu\nu}\,T^{\mu\nu}$, the whole classes of hybrid electromagnetic
solutions, and also wide classes of stationary solutions are derived for a
third order nonlinear key equations. Certain of these families can be thought
of as black hole solutions. For the most general set of Einstein-Maxwell
equations, reducible to three non-linear equations for the three unknown
functions, two new classes of solutions-having anti-de Sitter spinning metric
limit-are derived. The relationship of various families with those reported by
different authors' solutions has been established. Among the classes of
solutions with cosmological constant a relevant place occupy: the electrostatic
and magnetostatic Peldan solutions, the stationary uniform and spinning Clement
classes, the constant electromagnetic invariant branches with the particular
Kamata-Koikawa solution, the hybrid cyclic symmetric stationary black hole
fields, and the non-less important solutions generated via $SL(2,R)$
transformations where the Clement spinning charged solution, the
Martinez-Teitelboim-Zanelli black hole solution, and Dias-Lemos metric merit
mention.
| [
{
"created": "Thu, 25 Jul 2013 08:04:48 GMT",
"version": "v1"
}
] | 2015-06-16 | [
[
"Garcia-Diaz",
"Alberto A.",
""
]
] | From a general metric for stationary cyclic symmetric gravitational fields coupled to Maxwell electromagnetic fields within the $(2+1)$-dimensional gravity the uniqueness of wide families of exact solutions is established, among them, all uniform electromagnetic solutions possessing electromagnetic fields with vanishing covariant derivatives, all fields having constant electromagnetic invariants $F_{\mu\nu}\,F^{\mu\nu}$ and $T_{\mu\nu}\,T^{\mu\nu}$, the whole classes of hybrid electromagnetic solutions, and also wide classes of stationary solutions are derived for a third order nonlinear key equations. Certain of these families can be thought of as black hole solutions. For the most general set of Einstein-Maxwell equations, reducible to three non-linear equations for the three unknown functions, two new classes of solutions-having anti-de Sitter spinning metric limit-are derived. The relationship of various families with those reported by different authors' solutions has been established. Among the classes of solutions with cosmological constant a relevant place occupy: the electrostatic and magnetostatic Peldan solutions, the stationary uniform and spinning Clement classes, the constant electromagnetic invariant branches with the particular Kamata-Koikawa solution, the hybrid cyclic symmetric stationary black hole fields, and the non-less important solutions generated via $SL(2,R)$ transformations where the Clement spinning charged solution, the Martinez-Teitelboim-Zanelli black hole solution, and Dias-Lemos metric merit mention. |
2405.08659 | Armand Coudray | Armand Coudray | Conformal scattering of the wave equation in the Vaidya spacetime | null | null | null | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | We construct the conformal scattering operator for the scalar wave equation
on the Vaidya spacetime using vector field methods. The spacetime we consider
is Schwarzschild, near both past and future timelike infinities, in order to
use existing decay results for the scalar field, ensuring our energy estimates.
These estimates guarantee the injectivity of the trace operator and the closure
of its range. Finally, we solve a Goursat problem for the scalar waves on null
infinities, demonstrating that the range of the trace operator is dense.
Consequently, this implies that the scattering operator is an isomorphism.
| [
{
"created": "Tue, 14 May 2024 14:36:27 GMT",
"version": "v1"
}
] | 2024-05-15 | [
[
"Coudray",
"Armand",
""
]
] | We construct the conformal scattering operator for the scalar wave equation on the Vaidya spacetime using vector field methods. The spacetime we consider is Schwarzschild, near both past and future timelike infinities, in order to use existing decay results for the scalar field, ensuring our energy estimates. These estimates guarantee the injectivity of the trace operator and the closure of its range. Finally, we solve a Goursat problem for the scalar waves on null infinities, demonstrating that the range of the trace operator is dense. Consequently, this implies that the scattering operator is an isomorphism. |
gr-qc/9909028 | Leonardo Castellani | Leonardo Castellani | Gravity on Finite Groups | LaTeX, 26 pages, 1 figure. Corrected misprints and formula giving
exterior product of n 1-forms. Added note on topological action | Commun.Math.Phys. 218 (2001) 609-632 | 10.1007/s002200100409 | DFTT-44/99 | gr-qc hep-th | null | Gravity theories are constructed on finite groups G. A self-consistent review
of the differential calculi on finite G is given, with some new developments.
The example of a bicovariant differential calculus on the nonabelian finite
group S_3 is treated in detail, and used to build a gravity-like field theory
on S_3.
| [
{
"created": "Tue, 7 Sep 1999 17:55:25 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Jul 2000 16:54:16 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Castellani",
"Leonardo",
""
]
] | Gravity theories are constructed on finite groups G. A self-consistent review of the differential calculi on finite G is given, with some new developments. The example of a bicovariant differential calculus on the nonabelian finite group S_3 is treated in detail, and used to build a gravity-like field theory on S_3. |
gr-qc/0702042 | Jerry B. Griffiths | J. B. Griffiths and J. Podolsky | On the parameters of the Kerr-NUT-(anti-)de Sitter space-time | 4 pages. To appear as a Note in Classical and Quantum Gravity | Class.Quant.Grav.24:1687-1690,2007 | 10.1088/0264-9381/24/6/N02 | null | gr-qc hep-th | null | Different forms of the metric for the Kerr-NUT-(anti-)de Sitter space-time
are being widely used in its extension to higher dimensions. The purpose of
this note is to relate the parameters that are being used to the physical
parameters (mass, rotation, NUT and cosmological constant) in the basic four
dimensional situation.
| [
{
"created": "Wed, 7 Feb 2007 14:35:36 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Griffiths",
"J. B.",
""
],
[
"Podolsky",
"J.",
""
]
] | Different forms of the metric for the Kerr-NUT-(anti-)de Sitter space-time are being widely used in its extension to higher dimensions. The purpose of this note is to relate the parameters that are being used to the physical parameters (mass, rotation, NUT and cosmological constant) in the basic four dimensional situation. |
gr-qc/0401017 | Docteur Peter Wolf | Peter Wolf, Michael E. Tobar, Sebastien Bize, Andre Clairon, Andre N.
Luiten, Giorgio Santarelli | Whispering Gallery Resonators and Tests of Lorentz Invariance | 21 pages, 6 figures, accepted for General Relativity and Gravitation
(January, 2004). New version with slight changes following the referee's
suggestions | Gen.Rel.Grav. 36 (2004) 2352-2372 | 10.1023/B:GERG.0000046188.87741.51 | null | gr-qc astro-ph hep-ph | null | The frequencies of a cryogenic sapphire oscillator and a hydrogen maser are
compared to set new constraints on a possible violation of Lorentz invariance.
We give a detailed description of microwave resonators operating in Whispering
Gallery modes and then apply it to derive explicit models for Lorentz violating
effects in our experiment. Models are calculated in the theoretical framework
of Robertson, Mansouri and Sexl and in the standard model extension (SME) of
Kostelecky and co-workers. We constrain the parameters of the Mansouri and Sexl
test theory to $1/2 - \beta_{MS} + \delta_{MS} = (1.2 \pm 2.2) \times 10^{-9}$
and $\beta_{MS} - \alpha_{MS} - 1 = (1.6 \pm 3.0) \times 10^{-7}$ which is of
the same order as the best results from other experiments for the former and
represents a 70 fold improvement for the latter. These results correspond to an
improvement of our previously published limits [Wolf P. et al., Phys. Rev.
Lett. {\bf 90}, 6, 060402, (2003)] by about a factor 2.
| [
{
"created": "Tue, 6 Jan 2004 20:07:49 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Feb 2004 15:28:44 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Wolf",
"Peter",
""
],
[
"Tobar",
"Michael E.",
""
],
[
"Bize",
"Sebastien",
""
],
[
"Clairon",
"Andre",
""
],
[
"Luiten",
"Andre N.",
""
],
[
"Santarelli",
"Giorgio",
""
]
] | The frequencies of a cryogenic sapphire oscillator and a hydrogen maser are compared to set new constraints on a possible violation of Lorentz invariance. We give a detailed description of microwave resonators operating in Whispering Gallery modes and then apply it to derive explicit models for Lorentz violating effects in our experiment. Models are calculated in the theoretical framework of Robertson, Mansouri and Sexl and in the standard model extension (SME) of Kostelecky and co-workers. We constrain the parameters of the Mansouri and Sexl test theory to $1/2 - \beta_{MS} + \delta_{MS} = (1.2 \pm 2.2) \times 10^{-9}$ and $\beta_{MS} - \alpha_{MS} - 1 = (1.6 \pm 3.0) \times 10^{-7}$ which is of the same order as the best results from other experiments for the former and represents a 70 fold improvement for the latter. These results correspond to an improvement of our previously published limits [Wolf P. et al., Phys. Rev. Lett. {\bf 90}, 6, 060402, (2003)] by about a factor 2. |
gr-qc/0103022 | Winfried Zimdahl | Winfried Zimdahl (Konstanz) and Alexander B. Balakin (Kazan) | Conformal symmetry and deflationary gas universe | 10 pages, to appear in "Exact Solutions and Scalar Fields in Gravity:
Recent Developments", ed. by A. Macias, J. Cervantes-Cota, and C.
L\"ammerzahl, Kluwer Academic Publishers 2001 | null | 10.1007/0-306-47115-9_23 | null | gr-qc astro-ph hep-ph | null | We describe the ``deflationary'' evolution from an initial de Sitter phase to
a subsequent Friedmann-Lema\^{\i}tre-Robertson-Walker (FLRW) period as a
specific non-equilibrium configuration of a self-interacting gas. The
transition dynamics corresponds to a conformal, timelike symmetry of an
``optical'' metric, characterized by a refraction index of the cosmic medium
which continously decreases from a very large initial value to unity in the
FLRW phase.
| [
{
"created": "Thu, 8 Mar 2001 08:32:28 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Zimdahl",
"Winfried",
"",
"Konstanz"
],
[
"Balakin",
"Alexander B.",
"",
"Kazan"
]
] | We describe the ``deflationary'' evolution from an initial de Sitter phase to a subsequent Friedmann-Lema\^{\i}tre-Robertson-Walker (FLRW) period as a specific non-equilibrium configuration of a self-interacting gas. The transition dynamics corresponds to a conformal, timelike symmetry of an ``optical'' metric, characterized by a refraction index of the cosmic medium which continously decreases from a very large initial value to unity in the FLRW phase. |
2303.01165 | Johannes Kirsch | Johannes Kirsch, David Vasak, Armin van de Venn, J\"urgen Struckmeier | Torsion driving cosmic expansion | 26 pages, 3 figures | null | 10.1140/epjc/s10052-023-11571-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a cosmological model based on the canonical Hamiltonian
transformation theory. Using a linear-quadratic approach for the free
gravitational De Donder-Weyl Hamiltonian $H_\mathrm{Gr}$, the model contains
terms describing a deformation of an AdS spacetime and a fully anti-symmetric
torsion in addition to Einstein's theory. The resulting extension of the
Einstein-Cartan theory depends on two initially unknown constants,
$\Omega_\mathrm{g}$ and $\Omega_\mathrm{s}$. Given an appropriate choice of
these parameters resulting from the analysis of asymptotics, numerical
calculations were performed with $\Omega_\mathrm{\Lambda} = 0$. Values from the
Planck Collaboration were used for all other required cosmological parameters.
In this way, it is shown that torsion can explain phenomena commonly attributed
to dark energy, and thus can replace Einstein's cosmological constant.
| [
{
"created": "Thu, 2 Mar 2023 11:15:07 GMT",
"version": "v1"
}
] | 2023-06-07 | [
[
"Kirsch",
"Johannes",
""
],
[
"Vasak",
"David",
""
],
[
"van de Venn",
"Armin",
""
],
[
"Struckmeier",
"Jürgen",
""
]
] | We study a cosmological model based on the canonical Hamiltonian transformation theory. Using a linear-quadratic approach for the free gravitational De Donder-Weyl Hamiltonian $H_\mathrm{Gr}$, the model contains terms describing a deformation of an AdS spacetime and a fully anti-symmetric torsion in addition to Einstein's theory. The resulting extension of the Einstein-Cartan theory depends on two initially unknown constants, $\Omega_\mathrm{g}$ and $\Omega_\mathrm{s}$. Given an appropriate choice of these parameters resulting from the analysis of asymptotics, numerical calculations were performed with $\Omega_\mathrm{\Lambda} = 0$. Values from the Planck Collaboration were used for all other required cosmological parameters. In this way, it is shown that torsion can explain phenomena commonly attributed to dark energy, and thus can replace Einstein's cosmological constant. |
gr-qc/9306021 | null | Gerhard Rein and Alan D. Rendall | Global existence of classical solutions to the Vlasov-Poisson system in
a three dimensional, cosmological setting | 23 pages, Latex, report # 3 | null | 10.1007/BF00391558 | null | gr-qc | null | The initial value problem for the Vlasov-Poisson system is by now well
understood in the case of an isolated system where, by definition, the
distribution function of the particles as well as the gravitational potential
vanish at spatial infinity. Here we start with homogeneous solutions, which
have a spatially constant, non-zero mass density and which describe the mass
distribution in a Newtonian model of the universe. These homogeneous states can
be constructed explicitly, and we consider deviations from such homogeneous
states, which then satisfy a modified version of the Vlasov-Poisson system. We
prove global existence and uniqueness of classical solutions to the
corresponding initial value problem for initial data which represent spatially
periodic deviations from homogeneous states.
| [
{
"created": "Wed, 16 Jun 1993 09:20:00 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Rein",
"Gerhard",
""
],
[
"Rendall",
"Alan D.",
""
]
] | The initial value problem for the Vlasov-Poisson system is by now well understood in the case of an isolated system where, by definition, the distribution function of the particles as well as the gravitational potential vanish at spatial infinity. Here we start with homogeneous solutions, which have a spatially constant, non-zero mass density and which describe the mass distribution in a Newtonian model of the universe. These homogeneous states can be constructed explicitly, and we consider deviations from such homogeneous states, which then satisfy a modified version of the Vlasov-Poisson system. We prove global existence and uniqueness of classical solutions to the corresponding initial value problem for initial data which represent spatially periodic deviations from homogeneous states. |
0911.5597 | Alexander E. Shalyt-Margolin | A.E.Shalyt-Margolin | Entropy In The Present And Early Universe: New Small Parameters And Dark
Energy Problem | 29 pages, Latex. v.2. Minor correction. | Entropy 12:932-952,2010 | 10.3390/e12040932 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is demonstrated that entropy and its density play a significant role in
solving the problem of the vacuum energy density (cosmological constant) of the
Universe and hence the dark energy problem. Taking this in mind, two most
popular models for dark energy - Holographic Dark Energy Model and Agegraphic
Dark Energy Model - are analyzed. It is shown that the fundamental quantities
in the first of these models may be expressed in terms of a new small
dimensionless parameter. It is revealed that this parameter is naturally
occurring in High Energy Gravitational Thermodynamics and Gravitational
Holography (UV-limit). On this basis the possibility of a new approach to the
problem of Quantum Gravity is discussed. Besides, the results obtained on the
uncertainty relation of the pair "cosmological constant - volume of
space-time", where the cosmological constant is a dynamic quantity, are
reconsidered and generalized up to the Generalized Uncertainty Relation.
| [
{
"created": "Mon, 30 Nov 2009 09:55:06 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Apr 2010 04:39:26 GMT",
"version": "v2"
}
] | 2011-04-07 | [
[
"Shalyt-Margolin",
"A. E.",
""
]
] | It is demonstrated that entropy and its density play a significant role in solving the problem of the vacuum energy density (cosmological constant) of the Universe and hence the dark energy problem. Taking this in mind, two most popular models for dark energy - Holographic Dark Energy Model and Agegraphic Dark Energy Model - are analyzed. It is shown that the fundamental quantities in the first of these models may be expressed in terms of a new small dimensionless parameter. It is revealed that this parameter is naturally occurring in High Energy Gravitational Thermodynamics and Gravitational Holography (UV-limit). On this basis the possibility of a new approach to the problem of Quantum Gravity is discussed. Besides, the results obtained on the uncertainty relation of the pair "cosmological constant - volume of space-time", where the cosmological constant is a dynamic quantity, are reconsidered and generalized up to the Generalized Uncertainty Relation. |
2207.05907 | Zheng-Wen Long | S. R. Wu, B. Q. Wang, Z. W. Long | Probing Bardeen-Kiselev black hole with cosmological constant caused by
Einstein equations coupled with nonlinear electrodynamics using quasinormal
modes and greybody bounds | null | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we investigate a static and spherically symmetric
Bardeen-Kiselev black hole with cosmological constant which is a solution of
the Einstein-non-linear Maxwell field equations along with a quintessential
field. We compute the quasinormal frequencies for Bardeen-Kiselev black
hole(BH) with cosmological constant due to electromagnetic and gravitational
perturbations. By varying the BH parameters, we discuss the behaviour of both
real and imaginary parts of the BH quasinormal frequencies and compare
frequencies with Reissner-Nordstr\"om-de Sitter BH surrounded by quintessence
(RN-dSQ). Interestingly, it shows that the response of Bardeen-Kiselev BH with
cosmological constant and RN-dSQ under electromagnetic perturbations are
different when the charge parameter $q$, the state parameter $w$ and the
normalization factor $c$ are varied, but for the gravitational perturbations,
the response of Bardeen-Kiselev BH with cosmological constant and RN-dSQ are
different only when the charge parameter $q$ is varied. Therefore, compared
with the gravitational perturbations, the electromagnetic perturbations can be
used to understand nonlinear and linear electromagnetic fields in curved
spacetime separately. Another interesting observation is that due to the
presence of quintessence, the electromagnetic perturbations around the
Bardeen-Kiselev BH with cosmological constant damps faster and oscillates
slowly, and for the gravitational perturbations, the quasinormal mode decays
slowly and oscillates slowly. We also study the reflection and transmission
coefficients along with absorption cross section for the Bardeen-Kiselev BH
with cosmological constant, it shows that the transmission coefficients will
increase due to the presence of quintessence.
| [
{
"created": "Wed, 13 Jul 2022 01:04:26 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Nov 2022 16:49:16 GMT",
"version": "v2"
},
{
"created": "Fri, 28 Apr 2023 07:00:23 GMT",
"version": "v3"
},
{
"created": "Thu, 1 Jun 2023 16:30:25 GMT",
"version": "v4"
}
] | 2023-06-02 | [
[
"Wu",
"S. R.",
""
],
[
"Wang",
"B. Q.",
""
],
[
"Long",
"Z. W.",
""
]
] | In this work, we investigate a static and spherically symmetric Bardeen-Kiselev black hole with cosmological constant which is a solution of the Einstein-non-linear Maxwell field equations along with a quintessential field. We compute the quasinormal frequencies for Bardeen-Kiselev black hole(BH) with cosmological constant due to electromagnetic and gravitational perturbations. By varying the BH parameters, we discuss the behaviour of both real and imaginary parts of the BH quasinormal frequencies and compare frequencies with Reissner-Nordstr\"om-de Sitter BH surrounded by quintessence (RN-dSQ). Interestingly, it shows that the response of Bardeen-Kiselev BH with cosmological constant and RN-dSQ under electromagnetic perturbations are different when the charge parameter $q$, the state parameter $w$ and the normalization factor $c$ are varied, but for the gravitational perturbations, the response of Bardeen-Kiselev BH with cosmological constant and RN-dSQ are different only when the charge parameter $q$ is varied. Therefore, compared with the gravitational perturbations, the electromagnetic perturbations can be used to understand nonlinear and linear electromagnetic fields in curved spacetime separately. Another interesting observation is that due to the presence of quintessence, the electromagnetic perturbations around the Bardeen-Kiselev BH with cosmological constant damps faster and oscillates slowly, and for the gravitational perturbations, the quasinormal mode decays slowly and oscillates slowly. We also study the reflection and transmission coefficients along with absorption cross section for the Bardeen-Kiselev BH with cosmological constant, it shows that the transmission coefficients will increase due to the presence of quintessence. |
1201.2218 | Tiberiu Harko | Tiberiu Harko, Gabriela Mocanu | Stochastic oscillations of general relativistic disks | 10 pages, 8 figures, accepted for publication in MNRAS | Mon. Not. R. Astron. Soc., 421, 3102-3110 (2012) | 10.1111/j.1365-2966.2012.20530.x | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the general relativistic oscillations of thin accretion disks
around compact astrophysical objects interacting with the surrounding medium
through non-gravitational forces. The interaction with the external medium (a
thermal bath) is modeled via a friction force, and a random force,
respectively. The general equations describing the stochastically perturbed
disks are derived by considering the perturbations of trajectories of the test
particles in equatorial orbits, assumed to move along the geodesic lines. By
taking into account the presence of a viscous dissipation and of a stochastic
force we show that the dynamics of the stochastically perturbed disks can be
formulated in terms of a general relativistic Langevin equation. The stochastic
energy transport equation is also obtained. The vertical oscillations of the
disks in the Schwarzschild and Kerr geometries are considered in detail, and
they are analyzed by numerically integrating the corresponding Langevin
equations. The vertical displacements, velocities and luminosities of the
stochastically perturbed disks are explicitly obtained for both the
Schwarzschild and the Kerr cases.
| [
{
"created": "Wed, 11 Jan 2012 02:14:59 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"Harko",
"Tiberiu",
""
],
[
"Mocanu",
"Gabriela",
""
]
] | We analyze the general relativistic oscillations of thin accretion disks around compact astrophysical objects interacting with the surrounding medium through non-gravitational forces. The interaction with the external medium (a thermal bath) is modeled via a friction force, and a random force, respectively. The general equations describing the stochastically perturbed disks are derived by considering the perturbations of trajectories of the test particles in equatorial orbits, assumed to move along the geodesic lines. By taking into account the presence of a viscous dissipation and of a stochastic force we show that the dynamics of the stochastically perturbed disks can be formulated in terms of a general relativistic Langevin equation. The stochastic energy transport equation is also obtained. The vertical oscillations of the disks in the Schwarzschild and Kerr geometries are considered in detail, and they are analyzed by numerically integrating the corresponding Langevin equations. The vertical displacements, velocities and luminosities of the stochastically perturbed disks are explicitly obtained for both the Schwarzschild and the Kerr cases. |
2301.10275 | Gregory Horndeski PhD | Gregory W. Horndeski | The Multiverse and Cosmic Procreation via Cofinsler Spaces -- or --
Being and Nothingness | 37 pages, no figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | In this paper I shall consider a scalar-scalar field theory with scalar field
phi on a four-dimensional manifold M, and a Lorentzian Cofinsler function f on
T*M. A particularly simple Lagrangian is chosen to govern this theory, and when
f is chosen to generate FLRW metrics on M the Lagrangian becomes a function of
phi and its first two time derivatives. The associated Hamiltonian is
third-order, and admits infinitely many vacuum solutions. These vacuum
solutions can be pieced together to generate a multiverse. This is done for
those FLRW spaces with k>0. So when time, t, is less than zero we have a
universe in which the t=constant spaces are 3-spheres with constant curvature
k. As time passes through zero the underlying 4-space splits into an infinity
of spaces (branches) with metric tensors that describe piecewise de Sitter
spaces until some cutoff time, which will, in general, be different for
different branches. After passing through the cutoff time all branches will
return to their original 4-space in which the t=constant spaces are of constant
curvature k, but will remain separate from all of the other branch universes.
The metric tensor for this multiverse is everywhere continuous, but experiences
discontinuous derivatives as the universe branches change between different de
Sitter spaces. Some questions I address using this formalism are: what is the
nature of matter when t<0; what happens to matter as time passes through t=0;
and what was the universe doing before the multiple universes came into
existence at t=0? The answers to these questions will help to explain the
paper's title. I shall also briefly discuss a possible means of quantizing
space, how inflation influences the basic cells that constitute space, and how
gravitons might act.
| [
{
"created": "Tue, 24 Jan 2023 19:16:13 GMT",
"version": "v1"
}
] | 2023-01-26 | [
[
"Horndeski",
"Gregory W.",
""
]
] | In this paper I shall consider a scalar-scalar field theory with scalar field phi on a four-dimensional manifold M, and a Lorentzian Cofinsler function f on T*M. A particularly simple Lagrangian is chosen to govern this theory, and when f is chosen to generate FLRW metrics on M the Lagrangian becomes a function of phi and its first two time derivatives. The associated Hamiltonian is third-order, and admits infinitely many vacuum solutions. These vacuum solutions can be pieced together to generate a multiverse. This is done for those FLRW spaces with k>0. So when time, t, is less than zero we have a universe in which the t=constant spaces are 3-spheres with constant curvature k. As time passes through zero the underlying 4-space splits into an infinity of spaces (branches) with metric tensors that describe piecewise de Sitter spaces until some cutoff time, which will, in general, be different for different branches. After passing through the cutoff time all branches will return to their original 4-space in which the t=constant spaces are of constant curvature k, but will remain separate from all of the other branch universes. The metric tensor for this multiverse is everywhere continuous, but experiences discontinuous derivatives as the universe branches change between different de Sitter spaces. Some questions I address using this formalism are: what is the nature of matter when t<0; what happens to matter as time passes through t=0; and what was the universe doing before the multiple universes came into existence at t=0? The answers to these questions will help to explain the paper's title. I shall also briefly discuss a possible means of quantizing space, how inflation influences the basic cells that constitute space, and how gravitons might act. |
gr-qc/0001081 | Jose David Sanabria Gomez | Vladimir S. Manko, Eckehard W. Mielke and Jos\'e D. Sanabria-G\'omez | Exact Solution for the Exterior Field of a Rotating Neutron Star | Accepted for publication in Phys. Rev. D as Rapid Communication. 8
pages, 2 eps figures | Phys.Rev.D61:081501,2000 | 10.1103/PhysRevD.61.081501 | null | gr-qc astro-ph | null | A four-parameter class of exact asymptotically flat solutions of the
Einstein-Maxwell equations involving only rational functions is presented. It
is able to describe the exterior field of a slowly or rapidly rotating neutron
star with poloidal magnetic field.
| [
{
"created": "Tue, 25 Jan 2000 17:40:48 GMT",
"version": "v1"
}
] | 2009-12-30 | [
[
"Manko",
"Vladimir S.",
""
],
[
"Mielke",
"Eckehard W.",
""
],
[
"Sanabria-Gómez",
"José D.",
""
]
] | A four-parameter class of exact asymptotically flat solutions of the Einstein-Maxwell equations involving only rational functions is presented. It is able to describe the exterior field of a slowly or rapidly rotating neutron star with poloidal magnetic field. |
1205.0400 | Sylvain Marsat | Luc Blanchet and Sylvain Marsat | Relativistic MOND theory based on the Khronon scalar field | 8 pages, to appear in the Proceedings of the Xth International
Conference on Gravitation, Astrophysics and Cosmology (ICGAC10, Vietnam 2011) | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate a model of modified gravity recovering the modified Newtonian
dynamics (MOND) in the non-relativistic limit, based on the introduction of a
preferred time foliation violating Lorentz invariance in the weak-field regime.
Lorentz-invariance violation has been studied in the framework of
Einstein-aether theory, the generalization of which, known as non-canonical
Einstein-aether theory, having been proposed as a relativistic formulation of
MOND. Our model can be seen as a minimal specialization to the hypersurface
orthogonal case, which allows a different interpretation in terms of the
preferred time : it can be either treated as a dynamical scalar field in a 4D
formulation, or chosen as the time coordinate in a 3+1 formulation. We discuss
the equivalence of the two points of view and the non-relativistic limit of the
model.
| [
{
"created": "Wed, 2 May 2012 12:13:04 GMT",
"version": "v1"
}
] | 2012-05-03 | [
[
"Blanchet",
"Luc",
""
],
[
"Marsat",
"Sylvain",
""
]
] | We investigate a model of modified gravity recovering the modified Newtonian dynamics (MOND) in the non-relativistic limit, based on the introduction of a preferred time foliation violating Lorentz invariance in the weak-field regime. Lorentz-invariance violation has been studied in the framework of Einstein-aether theory, the generalization of which, known as non-canonical Einstein-aether theory, having been proposed as a relativistic formulation of MOND. Our model can be seen as a minimal specialization to the hypersurface orthogonal case, which allows a different interpretation in terms of the preferred time : it can be either treated as a dynamical scalar field in a 4D formulation, or chosen as the time coordinate in a 3+1 formulation. We discuss the equivalence of the two points of view and the non-relativistic limit of the model. |
gr-qc/0103023 | Kalashnikov | V. L. Kalashnikov | Introduction to relativistic astrophysics and cosmology through Maple | LaTeX, 124 pages, 34 figures, maple2e.sty, worksheet is accessible on
http://www.geocities.com/optomaplev | null | null | null | gr-qc | null | The basics of the relativistic astrophysics including the celestial mechanics
in weak field, black holes and cosmological models are illustrated and analyzed
by means of Maple 6
| [
{
"created": "Thu, 8 Mar 2001 12:23:00 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kalashnikov",
"V. L.",
""
]
] | The basics of the relativistic astrophysics including the celestial mechanics in weak field, black holes and cosmological models are illustrated and analyzed by means of Maple 6 |
gr-qc/0604007 | Shintaro Sawayama | Shintaro Sawayama | A new way to solve Wheeler-DeWitt equation including black hole universe | 11 page, 1 figure | null | null | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the unsolved issues in the quantum gravity comes from the
Wheeler-DeWitt equation, which is second order functional derivative equation.
In this paper, we introduce a new method to solve the Wheeler-DeWitt equation.
Usually one treats the state functional of the space of 3-dimensional metrics,
which do not contain timelike metrics. However we can expand this state to the
state which has support on the space of spacetime metrics with using additional
constraint which requires the recovery of 4-dimensional quantum gravity.
Enlarging the support of the state functional of the spacetime metrics, we can
simply solve the usual Wheeler-DeWitt equation with the additional constraint.
Using this method we can solve some unsolved problems, such as the quantization
of the black hole.
| [
{
"created": "Tue, 4 Apr 2006 00:43:33 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Jul 2006 22:38:45 GMT",
"version": "v2"
},
{
"created": "Sun, 15 Jun 2008 04:43:14 GMT",
"version": "v3"
},
{
"created": "Thu, 27 Nov 2008 03:41:18 GMT",
"version": "v4"
}
] | 2008-11-27 | [
[
"Sawayama",
"Shintaro",
""
]
] | One of the unsolved issues in the quantum gravity comes from the Wheeler-DeWitt equation, which is second order functional derivative equation. In this paper, we introduce a new method to solve the Wheeler-DeWitt equation. Usually one treats the state functional of the space of 3-dimensional metrics, which do not contain timelike metrics. However we can expand this state to the state which has support on the space of spacetime metrics with using additional constraint which requires the recovery of 4-dimensional quantum gravity. Enlarging the support of the state functional of the spacetime metrics, we can simply solve the usual Wheeler-DeWitt equation with the additional constraint. Using this method we can solve some unsolved problems, such as the quantization of the black hole. |
2302.14858 | Boris Daszuta | Boris Daszuta | Spectrally-tuned compact finite-difference schemes with domain
decomposition and applications to numerical relativity | null | null | null | null | gr-qc cs.NA math.NA | http://creativecommons.org/licenses/by/4.0/ | Compact finite-difference (FD) schemes specify derivative approximations
implicitly, thus to achieve parallelism with domain-decomposition suitable
partitioning of linear systems is required. Consistent order of accuracy,
dispersion, and dissipation is crucial to maintain in wave propagation problems
such that deformation of the associated spectra of the discretized problems is
not too severe. In this work we consider numerically tuning spectral error, at
fixed formal order of accuracy to automatically devise new compact FD schemes.
Grid convergence tests indicate error reduction of at least an order of
magnitude over standard FD. A proposed hybrid matching-communication strategy
maintains the aforementioned properties under domain-decomposition. Under
evolution of linear wave-propagation problems utilizing exponential integration
or explicit Runge-Kutta methods improvement is found to remain robust. A first
demonstration that compact FD methods may be applied to the Z4c formulation of
numerical relativity is provided where we couple our header-only, templated C++
implementation to the highly performant GR-Athena++ code. Evolving Z4c on
test-bed problems shows at least an order in magnitude reduction in phase error
compared to FD for propagated metric components. Stable binary-black-hole
evolution utilizing compact FD together with improved convergence is also
demonstrated.
| [
{
"created": "Tue, 28 Feb 2023 18:57:09 GMT",
"version": "v1"
}
] | 2023-03-01 | [
[
"Daszuta",
"Boris",
""
]
] | Compact finite-difference (FD) schemes specify derivative approximations implicitly, thus to achieve parallelism with domain-decomposition suitable partitioning of linear systems is required. Consistent order of accuracy, dispersion, and dissipation is crucial to maintain in wave propagation problems such that deformation of the associated spectra of the discretized problems is not too severe. In this work we consider numerically tuning spectral error, at fixed formal order of accuracy to automatically devise new compact FD schemes. Grid convergence tests indicate error reduction of at least an order of magnitude over standard FD. A proposed hybrid matching-communication strategy maintains the aforementioned properties under domain-decomposition. Under evolution of linear wave-propagation problems utilizing exponential integration or explicit Runge-Kutta methods improvement is found to remain robust. A first demonstration that compact FD methods may be applied to the Z4c formulation of numerical relativity is provided where we couple our header-only, templated C++ implementation to the highly performant GR-Athena++ code. Evolving Z4c on test-bed problems shows at least an order in magnitude reduction in phase error compared to FD for propagated metric components. Stable binary-black-hole evolution utilizing compact FD together with improved convergence is also demonstrated. |
1101.0191 | Shinji Tsujikawa | Shinji Tsujikawa | Modified gravity models of dark energy | 52 pages, 8 figures, a lecture note in the book "Lectures on
Cosmology: Accelerated Expansion of the Universe (Lecture Notes in Physics)"
(published by Springer) | Lect.Notes Phys.800:99-145,2010 | 10.1007/978-3-642-10598-2_3 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review recent progress of modified gravity models of dark energy--based on
f(R) gravity, scalar-tensor theories, braneworld gravity, Galileon gravity, and
other theories. In f(R) gravity and Brans-Dicke theory it is possible to design
viable models consistent with local gravity constraints under a chameleon
mechanism, while satisfying conditions for the cosmological viability. The
Dvali-Gabadazde-Porrati braneworld model can be compatible with local gravity
constraints through a nonlinear field self-interaction arising from a
brane-bending mode, but the self-accelerating solution contains a ghost mode in
addition to the tension with observational data about the cosmic expansion
history. The extension of the field self-interaction to more general forms
satisfying a Galilean symmetry in the flat space-time allows a possibility to
avoid the appearance of ghosts and Laplacian instabilities, while the late-time
cosmic acceleration can be realized by the field kinetic energy. We study the
evolution of cosmological perturbations in those models to place constraints on
model parameters from the observations of large-scale structure, cosmic
microwave background, and weak lensing. We also briefly review other modified
gravitational models of dark energy-- such as those based on Gauss-Bonnet
gravity and Lorentz-violating theories.
| [
{
"created": "Fri, 31 Dec 2010 02:50:07 GMT",
"version": "v1"
}
] | 2011-02-01 | [
[
"Tsujikawa",
"Shinji",
""
]
] | We review recent progress of modified gravity models of dark energy--based on f(R) gravity, scalar-tensor theories, braneworld gravity, Galileon gravity, and other theories. In f(R) gravity and Brans-Dicke theory it is possible to design viable models consistent with local gravity constraints under a chameleon mechanism, while satisfying conditions for the cosmological viability. The Dvali-Gabadazde-Porrati braneworld model can be compatible with local gravity constraints through a nonlinear field self-interaction arising from a brane-bending mode, but the self-accelerating solution contains a ghost mode in addition to the tension with observational data about the cosmic expansion history. The extension of the field self-interaction to more general forms satisfying a Galilean symmetry in the flat space-time allows a possibility to avoid the appearance of ghosts and Laplacian instabilities, while the late-time cosmic acceleration can be realized by the field kinetic energy. We study the evolution of cosmological perturbations in those models to place constraints on model parameters from the observations of large-scale structure, cosmic microwave background, and weak lensing. We also briefly review other modified gravitational models of dark energy-- such as those based on Gauss-Bonnet gravity and Lorentz-violating theories. |
2011.04229 | Daniel Berkowitz | Daniel Berkowitz | Towards Uncovering Generic Effects Of Matter Sources In Anisotropic
Quantum Cosmologies Via Taub Models | 53 pages, 21 figures and Mathematica code in the appendix | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We solve the Wheeler DeWitt equation for the Taub models in closed form when
both a cosmological constant and an electromagnetic field are present. In doing
so, we examine the 'excited states' of the quantum Taub models with the
aforementioned matter sources, and prove the existence of a countably infinite
number of 'excited' states. Additionally, we prove the existence of multiple
asymptotic solutions to the Lorentzian signature Wheeler DeWitt equation using
the Taub analogues of the 'wormhole', and 'no boundary' solutions of its
Euclidean-signature Hamilton Jacobi equation; we also study their 'excited
states. In the end we investigate qualitatively how our matter sources affect
the behavior of our wave functions and argue how these effects within the
context of quantum cosmology point to how a primordial electromagnetic field
could have played a profound role in the early universe.
| [
{
"created": "Mon, 9 Nov 2020 07:39:19 GMT",
"version": "v1"
}
] | 2020-11-10 | [
[
"Berkowitz",
"Daniel",
""
]
] | We solve the Wheeler DeWitt equation for the Taub models in closed form when both a cosmological constant and an electromagnetic field are present. In doing so, we examine the 'excited states' of the quantum Taub models with the aforementioned matter sources, and prove the existence of a countably infinite number of 'excited' states. Additionally, we prove the existence of multiple asymptotic solutions to the Lorentzian signature Wheeler DeWitt equation using the Taub analogues of the 'wormhole', and 'no boundary' solutions of its Euclidean-signature Hamilton Jacobi equation; we also study their 'excited states. In the end we investigate qualitatively how our matter sources affect the behavior of our wave functions and argue how these effects within the context of quantum cosmology point to how a primordial electromagnetic field could have played a profound role in the early universe. |
0706.1820 | Muhammad Sharif | M. Sharif | The Pseudo-Newtonian Force and Potential about a Higher Dimensional
Rotating Black Hole | 11 pages, accepted for publication in Nuovo Cimento B | Nuovo Cim.B122:343-350,2007 | 10.1393/ncb/i2007-10365-y | null | gr-qc | null | In this paper, we study the behavior of the pseudo-Newtonian force and
potential about a higher dimensional rotating black hole. We obtain conditions
for the force character from an attractive to repulsive. We also find the
conditions under which force attains a maximum value. The results of this paper
generalizes the already found structure of force and potential about a five
dimensional rotating black hole. It is interesting to note that we recover the
five dimensional results under a special case.
| [
{
"created": "Wed, 13 Jun 2007 04:50:01 GMT",
"version": "v1"
}
] | 2010-11-11 | [
[
"Sharif",
"M.",
""
]
] | In this paper, we study the behavior of the pseudo-Newtonian force and potential about a higher dimensional rotating black hole. We obtain conditions for the force character from an attractive to repulsive. We also find the conditions under which force attains a maximum value. The results of this paper generalizes the already found structure of force and potential about a five dimensional rotating black hole. It is interesting to note that we recover the five dimensional results under a special case. |
1906.03146 | Martin Bojowald | Martin Bojowald | Properties of fluctuating states in loop quantum cosmology | 12 pages | Mathematics 7 (2019) 645 | 10.3390/math7070645 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In loop quantum cosmology, the values of volume fluctuations and correlations
determine whether the dynamics of an evolving state exhibits a bounce. Of
particular interest are states that are supported only on either the positive
or the negative part of the spectrum of the Hamiltonian that generates this
evolution. It is shown here that the restricted support on the spectrum does
not significantly limit the possible values of volume fluctuations.
| [
{
"created": "Fri, 7 Jun 2019 15:04:09 GMT",
"version": "v1"
}
] | 2020-01-06 | [
[
"Bojowald",
"Martin",
""
]
] | In loop quantum cosmology, the values of volume fluctuations and correlations determine whether the dynamics of an evolving state exhibits a bounce. Of particular interest are states that are supported only on either the positive or the negative part of the spectrum of the Hamiltonian that generates this evolution. It is shown here that the restricted support on the spectrum does not significantly limit the possible values of volume fluctuations. |
2007.00214 | Alexandre Le Tiec | Alexandre Le Tiec, Marc Casals | Spinning Black Holes Fall in Love | 7 pages; matches version accepted in Phys. Rev. Lett | Phys. Rev. Lett. 126, 131102 (2021) | 10.1103/PhysRevLett.126.131102 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The open question of whether a black hole can become tidally deformed by an
external gravitational field has profound implications for fundamental physics,
astrophysics and gravitational-wave astronomy. Love tensors characterize the
tidal deformability of compact objects such as astrophysical (Kerr) black holes
under an external static tidal field. We prove that all Love tensors vanish
identically for a Kerr black hole in the nonspinning limit or for an
axisymmetric tidal perturbation. In contrast to this result, we show that Love
tensors are generically nonzero for a spinning black hole. Specifically, to
linear order in the Kerr black hole spin and the weak perturbing tidal field,
we compute in closed form the Love tensors that couple the mass-type and
current-type quadrupole moments to the electric-type and magnetic-type
quadrupolar tidal fields. For a dimensionless spin ~ 0.1, the nonvanishing
quadrupolar Love tensors are ~ 0.002, thus showing that black holes are
particularly "rigid" compact objects.
| [
{
"created": "Wed, 1 Jul 2020 03:55:13 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Feb 2021 13:02:14 GMT",
"version": "v2"
}
] | 2021-04-02 | [
[
"Tiec",
"Alexandre Le",
""
],
[
"Casals",
"Marc",
""
]
] | The open question of whether a black hole can become tidally deformed by an external gravitational field has profound implications for fundamental physics, astrophysics and gravitational-wave astronomy. Love tensors characterize the tidal deformability of compact objects such as astrophysical (Kerr) black holes under an external static tidal field. We prove that all Love tensors vanish identically for a Kerr black hole in the nonspinning limit or for an axisymmetric tidal perturbation. In contrast to this result, we show that Love tensors are generically nonzero for a spinning black hole. Specifically, to linear order in the Kerr black hole spin and the weak perturbing tidal field, we compute in closed form the Love tensors that couple the mass-type and current-type quadrupole moments to the electric-type and magnetic-type quadrupolar tidal fields. For a dimensionless spin ~ 0.1, the nonvanishing quadrupolar Love tensors are ~ 0.002, thus showing that black holes are particularly "rigid" compact objects. |
0808.2597 | Stephen R. Lau | Stephen R. Lau (1), Harald P. Pfeiffer (2), and Jan S. Hesthaven (1)
((1) Brown, (2) Caltech) | IMEX evolution of scalar fields on curved backgrounds | 28 pages, uses revtex4. Revised in response to referee's report. One
numerical experiment added which incorporates perturbed initial data and
adaptive time-stepping | Commun. Comput. Phys., 6 (2009), pp. 1063-1094 | 10.4208/cicp.2009.v6.p1063 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspiral of binary black holes occurs over a time-scale of many orbits, far
longer than the dynamical time-scale of the individual black holes. Explicit
evolutions of a binary system therefore require excessively many time steps to
capture interesting dynamics. We present a strategy to overcome the
Courant-Friedrichs-Lewy condition in such evolutions, one relying on modern
implicit-explicit ODE solvers and multidomain spectral methods for elliptic
equations. Our analysis considers the model problem of a forced scalar field
propagating on a generic curved background. Nevertheless, we encounter and
address a number of issues pertinent to the binary black hole problem in full
general relativity. Specializing to the Schwarzschild geometry in Kerr-Schild
coordinates, we document the results of several numerical experiments testing
our strategy.
| [
{
"created": "Tue, 19 Aug 2008 17:56:25 GMT",
"version": "v1"
},
{
"created": "Sat, 27 Jun 2009 20:51:28 GMT",
"version": "v2"
}
] | 2015-05-13 | [
[
"Lau",
"Stephen R.",
"",
"Brown"
],
[
"Pfeiffer",
"Harald P.",
"",
"Caltech"
],
[
"Hesthaven",
"Jan S.",
"",
"Brown"
]
] | Inspiral of binary black holes occurs over a time-scale of many orbits, far longer than the dynamical time-scale of the individual black holes. Explicit evolutions of a binary system therefore require excessively many time steps to capture interesting dynamics. We present a strategy to overcome the Courant-Friedrichs-Lewy condition in such evolutions, one relying on modern implicit-explicit ODE solvers and multidomain spectral methods for elliptic equations. Our analysis considers the model problem of a forced scalar field propagating on a generic curved background. Nevertheless, we encounter and address a number of issues pertinent to the binary black hole problem in full general relativity. Specializing to the Schwarzschild geometry in Kerr-Schild coordinates, we document the results of several numerical experiments testing our strategy. |
2307.00649 | Quentin Baghi | Quentin Baghi, Nikolaos Karnesis, Jean-Baptiste Bayle, Marc
Besan\c{c}on, Henri Inchausp\'e | Uncovering stochastic gravitational-wave backgrounds with LISA | 5 pages, 1 figure, contribution to the 2023 Gravitation session of
the 57th Rencontres de Moriond | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Finding a stochastic gravitational-wave background (SGWB) of astrophysical or
primordial origin is one of the quests of current and future gravitational-wave
observatories. While detector networks such as LIGO-Virgo-Kagra or pulsar
timing arrays can use cross-correlations to tell instrumental noise and SGWB
apart, LISA is likely to be the only flying detector of its kind in 2035. This
particularity poses a challenge for data analysis. To tackle it, we present a
strategy based on Bayesian model selection. We use a flexible noise power
spectral density~(PSD) model and the knowledge of noise and signal transfer
functions to allow SGWBs detection when the noise PSD is unknown. With this
technique, we then probe the parameter space accessible by LISA for power-law
SGWB shapes.
| [
{
"created": "Sun, 2 Jul 2023 20:00:20 GMT",
"version": "v1"
}
] | 2023-07-04 | [
[
"Baghi",
"Quentin",
""
],
[
"Karnesis",
"Nikolaos",
""
],
[
"Bayle",
"Jean-Baptiste",
""
],
[
"Besançon",
"Marc",
""
],
[
"Inchauspé",
"Henri",
""
]
] | Finding a stochastic gravitational-wave background (SGWB) of astrophysical or primordial origin is one of the quests of current and future gravitational-wave observatories. While detector networks such as LIGO-Virgo-Kagra or pulsar timing arrays can use cross-correlations to tell instrumental noise and SGWB apart, LISA is likely to be the only flying detector of its kind in 2035. This particularity poses a challenge for data analysis. To tackle it, we present a strategy based on Bayesian model selection. We use a flexible noise power spectral density~(PSD) model and the knowledge of noise and signal transfer functions to allow SGWBs detection when the noise PSD is unknown. With this technique, we then probe the parameter space accessible by LISA for power-law SGWB shapes. |
1604.02140 | Mahamat Saleh | Mahamat Saleh, Bouetou Bouetou Thomas and Kofane Timoleon Crepin | Quasinormal modes and Hawking radiation of a Reissner-Nordstr\"om black
hole surrounded by quintessence | 7 pages, 6 figures | Astrophys Space Sci (2011) 333: 449-455 | 10.1007/s10509-011-0643-8 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate quasinormal modes (QNMs) and Hawking radiation of a
Reissner-Nordstr\"om black hole sur-rounded by quintessence. The
Wentzel-Kramers-Brillouin (WKB) method is used to evaluate the QNMs and the
rate of radiation. The results show that due to the interaction of the
quintessence with the background metric, the QNMs of the black hole damp more
slowly when increasing the density of quintessence and the black hole radiates
at slower rate.
| [
{
"created": "Wed, 6 Apr 2016 20:23:31 GMT",
"version": "v1"
}
] | 2016-04-11 | [
[
"Saleh",
"Mahamat",
""
],
[
"Thomas",
"Bouetou Bouetou",
""
],
[
"Crepin",
"Kofane Timoleon",
""
]
] | We investigate quasinormal modes (QNMs) and Hawking radiation of a Reissner-Nordstr\"om black hole sur-rounded by quintessence. The Wentzel-Kramers-Brillouin (WKB) method is used to evaluate the QNMs and the rate of radiation. The results show that due to the interaction of the quintessence with the background metric, the QNMs of the black hole damp more slowly when increasing the density of quintessence and the black hole radiates at slower rate. |
2308.07100 | William Wolf | William J. Wolf and James Read and Quentin Vigneron | The Non-Relativistic Geometric Trinity of Gravity | Updated version with minor changes | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The geometric trinity of gravity comprises three distinct formulations of
general relativity: (i) the standard formulation describing gravity in terms of
spacetime curvature, (ii) the teleparallel equivalent of general relativity
describing gravity in terms of spacetime torsion, and (iii) the symmetric
teleparallel equivalent of general relativity (STEGR) describing gravity in
terms of spacetime non-metricity. In this article, we complete a geometric
trinity of non-relativistic gravity, by (a) taking the non-relativistic limit
of STEGR to determine its non-relativistic analogue, and (b) demonstrating that
this non-metric theory is equivalent to the Newton--Cartan theory and its
teleparallel equivalent, i.e., the curvature and the torsion based
non-relativistic theories that are both geometrised versions of classical
Newtonian gravity.
| [
{
"created": "Mon, 14 Aug 2023 12:24:17 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Aug 2023 02:22:35 GMT",
"version": "v2"
},
{
"created": "Fri, 22 Dec 2023 22:54:30 GMT",
"version": "v3"
},
{
"created": "Sun, 4 Feb 2024 14:46:19 GMT",
"version": "v4"
}
] | 2024-02-06 | [
[
"Wolf",
"William J.",
""
],
[
"Read",
"James",
""
],
[
"Vigneron",
"Quentin",
""
]
] | The geometric trinity of gravity comprises three distinct formulations of general relativity: (i) the standard formulation describing gravity in terms of spacetime curvature, (ii) the teleparallel equivalent of general relativity describing gravity in terms of spacetime torsion, and (iii) the symmetric teleparallel equivalent of general relativity (STEGR) describing gravity in terms of spacetime non-metricity. In this article, we complete a geometric trinity of non-relativistic gravity, by (a) taking the non-relativistic limit of STEGR to determine its non-relativistic analogue, and (b) demonstrating that this non-metric theory is equivalent to the Newton--Cartan theory and its teleparallel equivalent, i.e., the curvature and the torsion based non-relativistic theories that are both geometrised versions of classical Newtonian gravity. |
0802.4443 | Alexander Silenko | Alexander J. Silenko | Classical and Quantum Spins in Curved Spacetimes | Invited lecture presented at the International conference devoted to
Myron Mathisson: his life, work, and influence on current research. 23 pages | Acta Physica Polonica B Proc. Suppl. 1:87-107,2008 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A comparative analysis of the Mathisson-Papapetrou and Pomeransky-Khriplovich
equations is presented. Motion of spinning particles and their spins in
gravitational fields and noninertial frames is considered. The angular velocity
of spin precession defined by the Pomeransky-Khriplovich equations depends on
the choice of the tetrad. The connection of such a dependence with the Thomas
precession is established. General properties of spin interactions with
gravitational fields are discussed. It is shown that dynamics of classical and
quantum spins in curved spacetimes is identical. A manifestation of the
equivalence principle in an evolution of the helicity is analyzed.
| [
{
"created": "Fri, 29 Feb 2008 18:08:47 GMT",
"version": "v1"
}
] | 2008-05-16 | [
[
"Silenko",
"Alexander J.",
""
]
] | A comparative analysis of the Mathisson-Papapetrou and Pomeransky-Khriplovich equations is presented. Motion of spinning particles and their spins in gravitational fields and noninertial frames is considered. The angular velocity of spin precession defined by the Pomeransky-Khriplovich equations depends on the choice of the tetrad. The connection of such a dependence with the Thomas precession is established. General properties of spin interactions with gravitational fields are discussed. It is shown that dynamics of classical and quantum spins in curved spacetimes is identical. A manifestation of the equivalence principle in an evolution of the helicity is analyzed. |
2102.11722 | Gamal G.L. Nashed | G.G.L.Nashed | New rotating AdS/dS black holes in $\mathrm{f(R)}$ gravity | 13 pages, 8 figures. arXiv admin note: text overlap with
arXiv:2012.05711 | Physics Letters B Volume 815, 2021, 136133 | 10.1016/j.physletb.2021.136133 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | It is known that general relativity (GR) theory is not consistent with the
latest observations. The modified gravity of GR known as $\mathrm{f(R)}$ where
$\mathrm{R}$ is the Ricci scalar, is considered to be a good candidate for
dealing with the anomalies present in classical GR. In this context, we study
static rotating uncharged anti-de Sitter and de Sitter (AdS and dS) black holes
(BHs) using $\mathrm{f(R)}$ theory without assuming any constraints on the
Ricci scalar or on $\mathrm{f(R)}$. We derive BH solutions depend on the
convolution function and deviate from the AdS/dS Schwarzschild BH solution of
GR. Although the field equations have no dependence on the cosmological
constant, the BHs are characterized by an effective cosmological constant that
depends on the convolution function. The asymptotic form of this BH solution
depends on the gravitational mass of the system and on extra terms that lead to
BHs being different from GR BHs but to correspond to GR BHs under certain
conditions. We also investigate how these extra terms are responsible for
making the singularities of the invariants milder than those of the GR BHs. We
study some physical properties of the BHs from the point of view of
thermodynamics and show that there is an outer event horizon in addition to the
inner Cauchy horizons. Among other things, we show that our BH solutions
satisfy the first law of thermodynamics. To check the stability of these BHs we
use the geodesic deviations and derive the stability conditions. Finally, using
the odd-type mode it is shown that all the derived BHs are stable and have a
radial speed equal to one.
| [
{
"created": "Mon, 22 Feb 2021 10:08:34 GMT",
"version": "v1"
}
] | 2021-02-24 | [
[
"Nashed",
"G. G. L.",
""
]
] | It is known that general relativity (GR) theory is not consistent with the latest observations. The modified gravity of GR known as $\mathrm{f(R)}$ where $\mathrm{R}$ is the Ricci scalar, is considered to be a good candidate for dealing with the anomalies present in classical GR. In this context, we study static rotating uncharged anti-de Sitter and de Sitter (AdS and dS) black holes (BHs) using $\mathrm{f(R)}$ theory without assuming any constraints on the Ricci scalar or on $\mathrm{f(R)}$. We derive BH solutions depend on the convolution function and deviate from the AdS/dS Schwarzschild BH solution of GR. Although the field equations have no dependence on the cosmological constant, the BHs are characterized by an effective cosmological constant that depends on the convolution function. The asymptotic form of this BH solution depends on the gravitational mass of the system and on extra terms that lead to BHs being different from GR BHs but to correspond to GR BHs under certain conditions. We also investigate how these extra terms are responsible for making the singularities of the invariants milder than those of the GR BHs. We study some physical properties of the BHs from the point of view of thermodynamics and show that there is an outer event horizon in addition to the inner Cauchy horizons. Among other things, we show that our BH solutions satisfy the first law of thermodynamics. To check the stability of these BHs we use the geodesic deviations and derive the stability conditions. Finally, using the odd-type mode it is shown that all the derived BHs are stable and have a radial speed equal to one. |
gr-qc/0601014 | Maciej Dunajski | Maciej Dunajski | Einstein--Maxwell--Dilaton metrics from three--dimensional
Einstein--Weyl structures | 12 pages, to be published in Class.Quantum Grav | Class.Quant.Grav.23:2833-2840,2006 | 10.1088/0264-9381/23/9/004 | DAMTP-2006-3, NI06003-GMR | gr-qc hep-th nlin.SI | null | A class of time dependent solutions to $(3+1)$ Einstein--Maxwell-dilaton
theory with attractive electric force is found from Einstein--Weyl structures
in (2+1) dimensions corresponding to dispersionless Kadomtsev--Petviashvili and
$SU(\infty)$ Toda equations. These solutions are obtained from time--like
Kaluza--Klein reductions of $(3+2)$ solitons.
| [
{
"created": "Wed, 4 Jan 2006 15:37:53 GMT",
"version": "v1"
},
{
"created": "Sun, 12 Feb 2006 19:42:31 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Dunajski",
"Maciej",
""
]
] | A class of time dependent solutions to $(3+1)$ Einstein--Maxwell-dilaton theory with attractive electric force is found from Einstein--Weyl structures in (2+1) dimensions corresponding to dispersionless Kadomtsev--Petviashvili and $SU(\infty)$ Toda equations. These solutions are obtained from time--like Kaluza--Klein reductions of $(3+2)$ solitons. |
1610.09477 | Reza Saffari | Sara Dastan, Reza Saffari and Saheb Soroushfar | Shadow of a Kerr-Sen dilaton-axion Black Hole | 20 pages, 6 figures, 3 tables | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the shadow of charged stationary axially symmetric space-time
(Kerr-Sen dilaton-axion black hole). This black hole is defined by a mass $M$,
a spin $a$ and $r_{\alpha}=Q^{2}/M$, where $Q$ is the electric charge. Shadows
are investigated in two conditions, i) for an observer at infinity in vacuum
and ii) for an observer at infinity in the presence of plasma with radial
power-low density. In vacuum, the shadow of this black hole depends on charge
and spin parameter. We can see that, increasing electric charge, $Q$ decreases
the size of shadow. Also, increasing spin parameter $a$ decreases the size of
shadow. However, in existence of plasma, parameter of plasma like refraction
index, $n$, playing an important role on shadows. In fact, decreasing
refraction index decreases the size of shadow.
| [
{
"created": "Sat, 29 Oct 2016 09:11:41 GMT",
"version": "v1"
}
] | 2016-11-01 | [
[
"Dastan",
"Sara",
""
],
[
"Saffari",
"Reza",
""
],
[
"Soroushfar",
"Saheb",
""
]
] | We analyze the shadow of charged stationary axially symmetric space-time (Kerr-Sen dilaton-axion black hole). This black hole is defined by a mass $M$, a spin $a$ and $r_{\alpha}=Q^{2}/M$, where $Q$ is the electric charge. Shadows are investigated in two conditions, i) for an observer at infinity in vacuum and ii) for an observer at infinity in the presence of plasma with radial power-low density. In vacuum, the shadow of this black hole depends on charge and spin parameter. We can see that, increasing electric charge, $Q$ decreases the size of shadow. Also, increasing spin parameter $a$ decreases the size of shadow. However, in existence of plasma, parameter of plasma like refraction index, $n$, playing an important role on shadows. In fact, decreasing refraction index decreases the size of shadow. |
2007.09144 | Wei-Chen Lin | Wei-Chen Lin, William H. Kinney | The Trans-Planckian problem in Tachyacoustic Cosmology | 6 pages, 1 figure (v2: new section added.) | null | 10.1088/1475-7516/2021/04/044 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study Tachyacoustic models of cosmology, for which a scale-invariant
perturbation spectrum is generated via superluminal sound speed instead of
accelerated expansion, as in the case of inflation. We derive two bounds on the
size of acoustic horizon which constrain the duration of tachyacoustic
evolution, and therefore generation of primordial perturbations. We show that
existing models cannot solve the horizon problem without violating the
condition that all physical scales -- such as the Hubble parameter, the
pressure, and the length scale at which quantum modes freeze out and become
classical -- be sub-Planckian.
| [
{
"created": "Thu, 16 Jul 2020 23:26:51 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Sep 2020 19:06:12 GMT",
"version": "v2"
}
] | 2021-04-28 | [
[
"Lin",
"Wei-Chen",
""
],
[
"Kinney",
"William H.",
""
]
] | We study Tachyacoustic models of cosmology, for which a scale-invariant perturbation spectrum is generated via superluminal sound speed instead of accelerated expansion, as in the case of inflation. We derive two bounds on the size of acoustic horizon which constrain the duration of tachyacoustic evolution, and therefore generation of primordial perturbations. We show that existing models cannot solve the horizon problem without violating the condition that all physical scales -- such as the Hubble parameter, the pressure, and the length scale at which quantum modes freeze out and become classical -- be sub-Planckian. |
1001.0475 | Saibal Ray | Utpal Mukhopadhyay, Partha Pratim Ghosh and Saibal Ray | Higher Dimensional Dark Energy Investigation with Variable $\Lambda$ and
$G$ | 7 Latex pages with few changes | Int.J.Theor.Phys.49:1622-1627,2010 | 10.1007/s10773-010-0344-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Time variable $\Lambda$ and $G$ are studied here under a phenomenological
model of $\Lambda$ through an ($n+2$) dimensional analysis. The relation of
Zeldovich (1968) $|\Lambda| = 8\pi G^2m_p^6/h^4$ between $\Lambda$ and $G$ is
employed here, where $m_p$ is the proton mass and $h$ is Planck's constant. In
the present investigation some key issues of modern cosmology, viz. the age
problem, the amount of variation of $G$ and the nature of expansion of the
Universe have been addressed.
| [
{
"created": "Mon, 4 Jan 2010 11:43:03 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Mukhopadhyay",
"Utpal",
""
],
[
"Ghosh",
"Partha Pratim",
""
],
[
"Ray",
"Saibal",
""
]
] | Time variable $\Lambda$ and $G$ are studied here under a phenomenological model of $\Lambda$ through an ($n+2$) dimensional analysis. The relation of Zeldovich (1968) $|\Lambda| = 8\pi G^2m_p^6/h^4$ between $\Lambda$ and $G$ is employed here, where $m_p$ is the proton mass and $h$ is Planck's constant. In the present investigation some key issues of modern cosmology, viz. the age problem, the amount of variation of $G$ and the nature of expansion of the Universe have been addressed. |
1703.00222 | Davood Momeni Dr | Davood Momeni, Sudhaker Upadhyay, Yerlan Myrzakulov, Ratbay Myrzakulov | Cosmic string in gravity's rainbow | accepted in "Astrophys Space Sci" | Astrophys Space Sci (2017) 362:148 | 10.1007/s10509-017-3138-4 | EICTP-17-003 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the various cylindrical solutions (cosmic strings) in
gravity's rainbow scenario. In particular, we calculate the gravitational field
equations corresponding to energy-dependent background. Further, we discuss the
possible Kasner, quasi-Kasner and non-Kasner exact solutions of the field
equations. In this framework, we find that quasi-Kasner solutions can not be
realized in gravity's rainbow. Assuming only time-dependent metric functions,
we also analyse the time-dependent vacuum cosmic strings in gravity's rainbow,
which are completely different than the other GR solutions.
| [
{
"created": "Wed, 1 Mar 2017 10:44:33 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Mar 2017 04:07:28 GMT",
"version": "v2"
},
{
"created": "Sat, 29 Jul 2017 12:53:58 GMT",
"version": "v3"
}
] | 2017-08-03 | [
[
"Momeni",
"Davood",
""
],
[
"Upadhyay",
"Sudhaker",
""
],
[
"Myrzakulov",
"Yerlan",
""
],
[
"Myrzakulov",
"Ratbay",
""
]
] | In this paper, we study the various cylindrical solutions (cosmic strings) in gravity's rainbow scenario. In particular, we calculate the gravitational field equations corresponding to energy-dependent background. Further, we discuss the possible Kasner, quasi-Kasner and non-Kasner exact solutions of the field equations. In this framework, we find that quasi-Kasner solutions can not be realized in gravity's rainbow. Assuming only time-dependent metric functions, we also analyse the time-dependent vacuum cosmic strings in gravity's rainbow, which are completely different than the other GR solutions. |
1607.08888 | David Anderson | David Anderson, Nicolas Yunes, Enrico Barausse | The Effect of Cosmological Evolution on Solar System Constraints and on
the Scalarization of Neutron Stars in Massless Scalar-Tensor Theories | 15 pages, 9 figures | Phys. Rev. D 94, 104064 (2016) | 10.1103/PhysRevD.94.104064 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Certain scalar-tensor theories of gravity that generalize
Jordan-Fierz-Brans-Dicke theory are known to predict non-trivial phenomenology
for neutron stars. In these theories, first proposed by Damour and
Esposito-Far\`ese, the scalar field has a standard kinetic term, and couples
conformally to the matter fields. The weak equivalence principle is therefore
satisfied, but scalar effects may arise in strong-field regimes, e.g. allowing
for violations of the strong equivalence principle in neutron stars
("spontaneous scalarization") or in sufficiently tight binary neutron-star
systems ("dynamical/induced scalarization"). The original scalar-tensor theory
proposed by Damour and Esposito-Far\`ese is in tension with solar-system
constraints (for couplings that lead to scalarization), if one accounts for
cosmological evolution of the scalar field and no mass term is included in the
action. We here extend the conformal coupling of that theory, in order to
ascertain if, in this way, solar-system tests can be passed, while retaining a
non-trivial phenomenology for neutron stars. We find that even with this
generalized conformal coupling, it is impossible to construct a theory that
passes both Big-Bang nucleosynthesis and solar-system constraints, while
simultaneously allowing for scalarization in isolated/binary neutron stars.
| [
{
"created": "Fri, 29 Jul 2016 18:30:19 GMT",
"version": "v1"
}
] | 2016-12-07 | [
[
"Anderson",
"David",
""
],
[
"Yunes",
"Nicolas",
""
],
[
"Barausse",
"Enrico",
""
]
] | Certain scalar-tensor theories of gravity that generalize Jordan-Fierz-Brans-Dicke theory are known to predict non-trivial phenomenology for neutron stars. In these theories, first proposed by Damour and Esposito-Far\`ese, the scalar field has a standard kinetic term, and couples conformally to the matter fields. The weak equivalence principle is therefore satisfied, but scalar effects may arise in strong-field regimes, e.g. allowing for violations of the strong equivalence principle in neutron stars ("spontaneous scalarization") or in sufficiently tight binary neutron-star systems ("dynamical/induced scalarization"). The original scalar-tensor theory proposed by Damour and Esposito-Far\`ese is in tension with solar-system constraints (for couplings that lead to scalarization), if one accounts for cosmological evolution of the scalar field and no mass term is included in the action. We here extend the conformal coupling of that theory, in order to ascertain if, in this way, solar-system tests can be passed, while retaining a non-trivial phenomenology for neutron stars. We find that even with this generalized conformal coupling, it is impossible to construct a theory that passes both Big-Bang nucleosynthesis and solar-system constraints, while simultaneously allowing for scalarization in isolated/binary neutron stars. |
2206.13925 | Jose M. M. Senovilla | Jos\'e M M Senovilla | The influence of Penrose's singularity theorem in General Relativity | 34 pages, 4 figures. Based on my contribution `The 1965 singularity
theorem and its legacy' to the conference "Singularity theorems, causality,
and all that: A tribute to Roger Penrose" (SCRI21), June 14-18, 2021. To
appear in the topical volume `Singularity theorems, causality, and all that
(SCRI21)' https://link.springer.com/collections/hjjgajaagg. Improvements
suggested by referees | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Penrose's crucial contributions to General Relativity, symbolized by his 1965
singularity theorem, received (half of) the 2020 Nobel prize in Physics. A
renewed interest in the ideas and implications behind that theorem, its later
developments, and other Penrose's ideas improving our understanding of the
gravitational field thereby emerged. In this paper I highlight some of the
advancements motivated by the theorem that were developed over the years. I
also identify some common misconceptions about the theorem's implications. A
modern perspective on the concept of closed trapped submanifolds, based on the
mean curvature vector, is advocated.
| [
{
"created": "Tue, 28 Jun 2022 11:58:37 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Oct 2022 09:52:57 GMT",
"version": "v2"
}
] | 2022-10-11 | [
[
"Senovilla",
"José M M",
""
]
] | Penrose's crucial contributions to General Relativity, symbolized by his 1965 singularity theorem, received (half of) the 2020 Nobel prize in Physics. A renewed interest in the ideas and implications behind that theorem, its later developments, and other Penrose's ideas improving our understanding of the gravitational field thereby emerged. In this paper I highlight some of the advancements motivated by the theorem that were developed over the years. I also identify some common misconceptions about the theorem's implications. A modern perspective on the concept of closed trapped submanifolds, based on the mean curvature vector, is advocated. |
1912.09449 | Juri Smirnov | Marvin L\"uben, Angnis Schmidt-May and Juri Smirnov | Vainshtein Screening in Bimetric Cosmology | Version published in PRD, comments are welcome | Phys. Rev. D 102, 123529 (2020) | 10.1103/PhysRevD.102.123529 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We demonstrate that the instabilities in linear cosmological perturbations in
bimetric theory are the manifestation of the non-linear Vainshtein mechanism on
an FRW background. The spin-2 mass serves as the cosmological Vainshtein scale
in this case. This allows us to quantitatively address early universe
cosmology. In particular, in a global analysis, we study data from the cosmic
microwave background radiation and local measurements of the Hubble flow. We
show that bimetric cosmology resolves the discrepancy in the local and
early-time measurements of the Hubble scale via an effective phantom dark
energy component.
| [
{
"created": "Thu, 19 Dec 2019 18:25:08 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Nov 2020 23:33:56 GMT",
"version": "v2"
}
] | 2021-01-04 | [
[
"Lüben",
"Marvin",
""
],
[
"Schmidt-May",
"Angnis",
""
],
[
"Smirnov",
"Juri",
""
]
] | We demonstrate that the instabilities in linear cosmological perturbations in bimetric theory are the manifestation of the non-linear Vainshtein mechanism on an FRW background. The spin-2 mass serves as the cosmological Vainshtein scale in this case. This allows us to quantitatively address early universe cosmology. In particular, in a global analysis, we study data from the cosmic microwave background radiation and local measurements of the Hubble flow. We show that bimetric cosmology resolves the discrepancy in the local and early-time measurements of the Hubble scale via an effective phantom dark energy component. |
2302.04924 | Franco Fiorini | Franco Fiorini | Local symmetries in $f(T)$-like models: lessons from 2D | Contribution to be submitted to the Int. J. Geom. Methods Mod. Phys.
special issue "Metric-Affine Gravity at Tartu" | Int. J. Geom. Methods Mod. Phys. 2350183 (2023) | 10.1142/S0219887823501839 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The comprehension of the intricate structure associated to the local
symmetries encoded in the tetrad field, as well as its physical meaning, is
perhaps the most important unsolved problem within $f(T)$ gravity. This is
inextricably connected to the number, nature and potential impact that the
additional degree/s of freedom might have within these --and other closely
related--models of gravity in which the local Lorentz invariance is broken at
some level. Here we review and further explain some recent results which make
use of the more placid scenery provided by 2D-torsional models of gravity,
where the local symmetries adapted to a given geometry can be fully
characterized.
| [
{
"created": "Thu, 9 Feb 2023 20:41:09 GMT",
"version": "v1"
}
] | 2023-09-14 | [
[
"Fiorini",
"Franco",
""
]
] | The comprehension of the intricate structure associated to the local symmetries encoded in the tetrad field, as well as its physical meaning, is perhaps the most important unsolved problem within $f(T)$ gravity. This is inextricably connected to the number, nature and potential impact that the additional degree/s of freedom might have within these --and other closely related--models of gravity in which the local Lorentz invariance is broken at some level. Here we review and further explain some recent results which make use of the more placid scenery provided by 2D-torsional models of gravity, where the local symmetries adapted to a given geometry can be fully characterized. |
gr-qc/0411090 | Hing Tong Cho | H. T. Cho and Y.-C. Lin | WKB Analysis of the Scattering of Massive Dirac Fields in Schwarzschild
Black Hole Spacetimes | 21 pages, 8 figures | Class.Quant.Grav. 22 (2005) 775-790 | 10.1088/0264-9381/22/5/001 | null | gr-qc hep-th | null | We analysis the radial equations for massive Dirac fields in Schwarzschild
black hole spacetimes. Different approximation formulae under the WKB scheme
are developed for the transmission probability ${\cal T}$ of the radial
wavefunction with $E^{2}\gg V_{m}$, $E^{2}\approx V_{m}$, and $E^{2}\ll V_{m}$,
where $E$ is the energy of the field and $V_{m}$ is the maximum value of the
effective potential. Explicit results of ${\cal T}$ in these approximations are
given for various values of $E$, the mass $m$, and the angular momentum
parameter $\kappa$ of the fields. We also discuss the dependence of ${\cal T}$
on these parameters.
| [
{
"created": "Thu, 18 Nov 2004 02:08:56 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Cho",
"H. T.",
""
],
[
"Lin",
"Y. -C.",
""
]
] | We analysis the radial equations for massive Dirac fields in Schwarzschild black hole spacetimes. Different approximation formulae under the WKB scheme are developed for the transmission probability ${\cal T}$ of the radial wavefunction with $E^{2}\gg V_{m}$, $E^{2}\approx V_{m}$, and $E^{2}\ll V_{m}$, where $E$ is the energy of the field and $V_{m}$ is the maximum value of the effective potential. Explicit results of ${\cal T}$ in these approximations are given for various values of $E$, the mass $m$, and the angular momentum parameter $\kappa$ of the fields. We also discuss the dependence of ${\cal T}$ on these parameters. |
gr-qc/9901062 | Dominic Clancy | Dominic Clancy, Alexander Feinstein, James E. Lidsey and Reza Tavakol | Inhomogeneous Einstein-Rosen String Cosmology | Minor extension of concluding section; 18 pages, to appear in
Phys.Rev. D | Phys.Rev. D60 (1999) 043503 | 10.1103/PhysRevD.60.043503 | null | gr-qc hep-th | null | Families of anisotropic and inhomogeneous string cosmologies containing
non-trivial dilaton and axion fields are derived by applying the global
symmetries of the string effective action to a generalized Einstein-Rosen
metric. The models exhibit a two-dimensional group of Abelian isometries. In
particular, two classes of exact solutions are found that represent
inhomogeneous generalizations of the Bianchi type VI_h cosmology. The
asymptotic behaviour of the solutions is investigated and further applications
are briefly discussed.
| [
{
"created": "Fri, 22 Jan 1999 19:11:14 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Jan 1999 20:22:42 GMT",
"version": "v2"
},
{
"created": "Thu, 6 May 1999 13:22:45 GMT",
"version": "v3"
}
] | 2009-10-31 | [
[
"Clancy",
"Dominic",
""
],
[
"Feinstein",
"Alexander",
""
],
[
"Lidsey",
"James E.",
""
],
[
"Tavakol",
"Reza",
""
]
] | Families of anisotropic and inhomogeneous string cosmologies containing non-trivial dilaton and axion fields are derived by applying the global symmetries of the string effective action to a generalized Einstein-Rosen metric. The models exhibit a two-dimensional group of Abelian isometries. In particular, two classes of exact solutions are found that represent inhomogeneous generalizations of the Bianchi type VI_h cosmology. The asymptotic behaviour of the solutions is investigated and further applications are briefly discussed. |
1901.06617 | Shao-Wen Wei | Run Zhou, Shao-Wen Wei | Novel equal area law and analytical charge-electric potential
criticality for charged Anti-de Sitter black holes | 10 pages, 3 figures, structures are re-organized | Phys. Lett. B 792, 406 (2019) | 10.1016/j.physletb.2019.04.010 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the equal area law and charge-electric potential criticality for the
charged Anti-de Sitter black holes. Considering that the black hole charge is a
double-valued function of the electric potential, we investigate the equal area
law in detail. We find that the equal area law has two different expressions
when the thermodynamic quantities are near the critical point and far from the
critical point. For these two different cases, we obtain the analytical
coexistence curve for the low and high electric potential black hole phases by
using these two expressions of the equal area law. Based on the result, we
analytically study the phase diagram and the critical phenomena in the
charge-electric potential plane.
| [
{
"created": "Sun, 20 Jan 2019 03:14:02 GMT",
"version": "v1"
},
{
"created": "Wed, 29 May 2019 03:01:34 GMT",
"version": "v2"
}
] | 2019-05-30 | [
[
"Zhou",
"Run",
""
],
[
"Wei",
"Shao-Wen",
""
]
] | We study the equal area law and charge-electric potential criticality for the charged Anti-de Sitter black holes. Considering that the black hole charge is a double-valued function of the electric potential, we investigate the equal area law in detail. We find that the equal area law has two different expressions when the thermodynamic quantities are near the critical point and far from the critical point. For these two different cases, we obtain the analytical coexistence curve for the low and high electric potential black hole phases by using these two expressions of the equal area law. Based on the result, we analytically study the phase diagram and the critical phenomena in the charge-electric potential plane. |
1810.10585 | Ian Hinder | Ian Hinder, Serguei Ossokine, Harald P. Pfeiffer, Alessandra Buonanno | Gravitational waveforms for high spin and high mass-ratio binary black
holes: A synergistic use of numerical-relativity codes | 7 pages, 4 figures | Phys. Rev. D 99, 061501 (2019) | 10.1103/PhysRevD.99.061501 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Observation and characterisation of gravitational waves from binary black
holes requires accurate knowledge of the expected waveforms. The late inspiral
and merger phase of the waveform is obtained through direct numerical
integration of the full 3-dimensional Einstein equations. The Spectral Einstein
Code (SpEC) utilizes a multi-domain pseudo-spectral method tightly adapted to
the geometry of the black holes; it is computationally efficient and accurate,
but--for high mass-ratios and large spins--sometimes requires manual
fine-tuning for the merger-phase of binaries. The Einstein Toolkit (ET) employs
finite difference methods and the moving puncture technique; it is less
computationally efficient, but highly robust.
For some mergers with high mass ratio and large spins, the efficient
numerical algorithms used in SpEC have failed, whereas the simpler algorithms
used in the ET were successful. Given the urgent need of testing the accuracy
of waveform models currently used in LIGO and Virgo inference analyses for high
mass ratios and spins, we present here a synergistic approach to
numerical-relativity: We combine SpEC and ET waveforms into complete
inspiral-merger-ringdown waveforms, taking advantage of the computational
efficiency of the pseudo-spectral code during the inspiral, and the robustness
of the finite-difference code at the merger. We validate our method against a
case where complete waveforms from both codes are available, compute three new
hybrid numerical-relativity waveforms, and compare them with analytical
waveform models currently used in LIGO and Virgo science. All the waveforms and
the hybridization code are publicly available.
| [
{
"created": "Wed, 24 Oct 2018 19:38:27 GMT",
"version": "v1"
}
] | 2019-03-27 | [
[
"Hinder",
"Ian",
""
],
[
"Ossokine",
"Serguei",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Buonanno",
"Alessandra",
""
]
] | Observation and characterisation of gravitational waves from binary black holes requires accurate knowledge of the expected waveforms. The late inspiral and merger phase of the waveform is obtained through direct numerical integration of the full 3-dimensional Einstein equations. The Spectral Einstein Code (SpEC) utilizes a multi-domain pseudo-spectral method tightly adapted to the geometry of the black holes; it is computationally efficient and accurate, but--for high mass-ratios and large spins--sometimes requires manual fine-tuning for the merger-phase of binaries. The Einstein Toolkit (ET) employs finite difference methods and the moving puncture technique; it is less computationally efficient, but highly robust. For some mergers with high mass ratio and large spins, the efficient numerical algorithms used in SpEC have failed, whereas the simpler algorithms used in the ET were successful. Given the urgent need of testing the accuracy of waveform models currently used in LIGO and Virgo inference analyses for high mass ratios and spins, we present here a synergistic approach to numerical-relativity: We combine SpEC and ET waveforms into complete inspiral-merger-ringdown waveforms, taking advantage of the computational efficiency of the pseudo-spectral code during the inspiral, and the robustness of the finite-difference code at the merger. We validate our method against a case where complete waveforms from both codes are available, compute three new hybrid numerical-relativity waveforms, and compare them with analytical waveform models currently used in LIGO and Virgo science. All the waveforms and the hybridization code are publicly available. |
1006.2406 | Carlos Leiva | Carlos Leiva, Ignacio Espinoza | Effective Potential Structure of the BTZ Black Hole in Rainbow Gravity | 6 pages, 2 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study the effective potential structure of the BTZ black
hole in rainbow gravity for a massive and a massless particles.
| [
{
"created": "Fri, 11 Jun 2010 21:25:28 GMT",
"version": "v1"
}
] | 2010-06-15 | [
[
"Leiva",
"Carlos",
""
],
[
"Espinoza",
"Ignacio",
""
]
] | In this paper we study the effective potential structure of the BTZ black hole in rainbow gravity for a massive and a massless particles. |
1907.03606 | J\'er\'emie Francfort | J\'er\'emie Francfort, Basundhara Ghosh and Ruth Durrer | Cosmological Number Counts in Einstein and Jordan frames | 18 pages, 1 figure | null | 10.1088/1475-7516/2019/09/071 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Even though we know that physical observations are frame independent, the
frame dependence of cosmological perturbations is relatively subtle and has led
to confusion in the past. In this paper we show that while the (unobservable)
matter power spectrum is frame dependent, the observable number counts are not.
We shall also determine how the frame dependence of the power spectrum depends
on scale.
| [
{
"created": "Mon, 8 Jul 2019 13:31:34 GMT",
"version": "v1"
}
] | 2019-10-09 | [
[
"Francfort",
"Jérémie",
""
],
[
"Ghosh",
"Basundhara",
""
],
[
"Durrer",
"Ruth",
""
]
] | Even though we know that physical observations are frame independent, the frame dependence of cosmological perturbations is relatively subtle and has led to confusion in the past. In this paper we show that while the (unobservable) matter power spectrum is frame dependent, the observable number counts are not. We shall also determine how the frame dependence of the power spectrum depends on scale. |
0906.1769 | Alessandro Nagar | Thibault Damour and Alessandro Nagar | The Effective One Body description of the Two-Body problem | 45 pages, 11 figures. Lecture given at the "School on Mass" (Orleans,
France, June 2008), uses Springer's "svmult.cls" | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Effective One Body (EOB) formalism is an analytical approach which aims
at providing an accurate description of the motion and radiation of coalescing
binary black holes with arbitrary mass ratio. We review the basic elements of
this formalism and discuss its aptitude at providing accurate template
waveforms to be used for gravitational wave data analysis purposes.
| [
{
"created": "Tue, 9 Jun 2009 16:04:21 GMT",
"version": "v1"
}
] | 2009-06-10 | [
[
"Damour",
"Thibault",
""
],
[
"Nagar",
"Alessandro",
""
]
] | The Effective One Body (EOB) formalism is an analytical approach which aims at providing an accurate description of the motion and radiation of coalescing binary black holes with arbitrary mass ratio. We review the basic elements of this formalism and discuss its aptitude at providing accurate template waveforms to be used for gravitational wave data analysis purposes. |
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